Buggy python submission (verdict: Time Limit Exceeded):
H,W=map(int,input().split())

queue=[]
mat=[[True]*(W+2)]
for i in range(1,H+1):
  array=[True]+[x=="#" for x in input()]+[True]
  mat.append(array)
  for j in range(1,W+1):
    if array[j]:
      queue.append((i,j))
mat.append([True]*(W+2))
#print(mat)
#print(queue)

d=0
while queue:
  new_queue=set()
  for q in queue:
    i,j=q
    #print(q)
    if not mat[i-1][j]:
      new_queue.add((i-1,j))
      mat[i-1][j]=True
    if not mat[i+1][j]:
      new_queue.add((i+1,j))
      mat[i+1][j]=True
    if not mat[i][j-1]:
      new_queue.add((i,j-1))
      mat[i][j-1]=True
    if not mat[i][j+1]:
      new_queue.add((i,j+1))
      mat[i][j+1]=True
      
  queue=list(new_queue)
  d+=1
  
print(d-1)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
H,W=map(int,input().split())

mat=[[True]*(W+2)]
queue=set()
for i in range(H):
  a_str=input()
  for j in range(W):
    if a_str[j]=="#":
      queue.add((i+1,j+1))
      
  mat.append([True]+[a=="#" for a in a_str]+[True])
  
mat.append([True]*(W+2))

#print(mat)
#print(queue)

answer=0
while(True):
  new_queue=set()
  for q in queue:
    i,j=q
    #print(q)
    if not mat[i-1][j]:
      new_queue.add((i-1,j))
      mat[i-1][j]=True
    if not mat[i+1][j]:
      new_queue.add((i+1,j))
      mat[i+1][j]=True
    if not mat[i][j-1]:
      new_queue.add((i,j-1))
      mat[i][j-1]=True
    if not mat[i][j+1]:
      new_queue.add((i,j+1))
      mat[i][j+1]=True
      
  if len(new_queue)==0:
    break
  else:
    queue=new_queue
    answer+=1
  
print(answer)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      mark_matrix[i+1][j+1] = True
      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
mark_matrix += [[True]+[False]*(W)+[True] for _ in range(H)]
mark_matrix += [[True]*(W+2)]
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      mark_matrix[i+1][j+1] = True
      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)

#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
mark_matrix += [[False]*(W+2) for _ in range(H)]
mark_matrix += [[True]*(W+2)]
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      mark_matrix[i+1][j+1] = True
      queue.append((i+1,j+1))
for i in range(1,H+1):
  mark_matrix[i][0] = True
  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)

#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2) for _ in range(H+2)]
#queue = []
queue = deque()
for i in range(H):
  line = input().strip()
  for j,ch in enumerate(line):
    if ch == "#":
      queue.append((i+1,j+1))
    else:
      mark_matrix[i+1][j+1] = False
  
#print(mark_matrix)
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))

  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[False] *(W+2) for _ in range(H+2)]
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      mark_matrix[i+1][j+1] = True
      queue.append((i+1,j+1))
for i in range(H+2):
  mark_matrix[i][0] = True
  mark_matrix[i][W+1] = True
for j in range(W+2):
  mark_matrix[0][j] = True
  mark_matrix[H+1][j] = True
  
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))

  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[False] * W for _ in range(H)]
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      mark_matrix[i][j] = True
      queue.append((i,j))
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if i > 0 and not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if i < H-1 and not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if j > 0 and not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if j < W-1 and not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))

  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Runtime Error):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[False] * W for _ in range(H)]
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      mark_matrix[i][j] = True
      queue.append((i,j))
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if i > 0 and not dist_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if i < H-1 and not dist_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if j > 0 and not dist_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if j < W-1 and not dist_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))

  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
dist_matrix = [[-1] * W for _ in range(H)]
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      dist_matrix[i][j] = 0
      queue.append((i,j))
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  i,j = queue.popleft()
  max_value = dist_matrix[i][j]
  #cnt += 1
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = max_value + 1
    queue.append((i-1,j))
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = max_value + 1
    queue.append((i+1,j))
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = max_value + 1
    queue.append((i,j-1))
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = max_value + 1
    queue.append((i,j+1))
 
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
#dist_matrix = [[-1] * W for _ in range(H)]
dist_hash = {}
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      #dist_matrix[i][j] = 0
      dist_hash[i*W+j] = 0
      queue.append(i*W+j)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  ij = queue.popleft()
  i = ij//W
  j = ij%W
  #max_value = dist_matrix[i][j]
  max_value = dist_hash[i*W+j]
  #cnt += 1
  #if i > 0 and dist_matrix[i-1][j] == -1:
  if i > 0 and (i-1)*W+j not in dist_hash:
    #dist_matrix[i-1][j] = max_value + 1
    dist_hash[(i-1)*W+j] = max_value + 1
    queue.append((i-1)*W+j)
  #if i < H-1 and dist_matrix[i+1][j] == -1:
  if i < H-1 and (i+1)*W+j not in dist_hash:
    #dist_matrix[i+1][j] = max_value + 1
    dist_hash[(i+1)*W+j] = max_value + 1
    queue.append((i+1)*W+j)
  #if j > 0 and dist_matrix[i][j-1] == -1:
  if j > 0 and i*W+j-1 not in dist_hash:
    #dist_matrix[i][j-1] = max_value + 1
    dist_hash[i*W+j-1] = max_value + 1
    queue.append(i*W+j-1)
  #if j < W-1 and dist_matrix[i][j+1] == -1:
  if j < W-1 and i*W+j+1 not in dist_hash:
    #dist_matrix[i][j+1] = max_value + 1
    dist_hash[i*W+j+1] = max_value + 1
    queue.append(i*W+j+1)
 
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
#dist_matrix = [[-1] * W for _ in range(H)]
dist_hash = {}
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      #dist_matrix[i][j] = 0
      dist_hash[i*W+j] = 0
      queue.append([i,j])
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  i,j = queue.popleft()
  #max_value = dist_matrix[i][j]
  max_value = dist_hash[i*W+j]
  #cnt += 1
  #if i > 0 and dist_matrix[i-1][j] == -1:
  if i > 0 and (i-1)*W+j not in dist_hash:
    #dist_matrix[i-1][j] = max_value + 1
    dist_hash[(i-1)*W+j] = max_value + 1
    queue.append([i-1,j])
  #if i < H-1 and dist_matrix[i+1][j] == -1:
  if i < H-1 and (i+1)*W+j not in dist_hash:
    #dist_matrix[i+1][j] = max_value + 1
    dist_hash[(i+1)*W+j] = max_value + 1
    queue.append([i+1,j])
  #if j > 0 and dist_matrix[i][j-1] == -1:
  if j > 0 and i*W+j-1 not in dist_hash:
    #dist_matrix[i][j-1] = max_value + 1
    dist_hash[i*W+j-1] = max_value + 1
    queue.append([i,j-1])
  #if j < W-1 and dist_matrix[i][j+1] == -1:
  if j < W-1 and i*W+j+1 not in dist_hash:
    #dist_matrix[i][j+1] = max_value + 1
    dist_hash[i*W+j+1] = max_value + 1
    queue.append([i,j+1])
 
#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque
import sys
input = sys.stdin.readline

H, W = map(int, input().split())
dist_matrix = [[-1] * W for _ in range(H)]
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      dist_matrix[i][j] = 0
      queue.append([i,j])

#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  i,j = queue.popleft()
  max_value = dist_matrix[i][j]
  #cnt += 1
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = max_value + 1
    queue.append([i-1,j])
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = max_value + 1
    queue.append([i+1,j])
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = max_value + 1
    queue.append([i,j-1])
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = max_value + 1
    queue.append([i,j+1])

#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

H, W = map(int, input().split())
dist_matrix = [[-1] * W for i in range(H)]
#queue = []
queue = deque()
for i in range(H):
  line = input()
  for j,ch in enumerate(line):
    if ch == "#":
      dist_matrix[i][j] = 0
      queue.append([i,j])

#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  i,j = queue.popleft()
  max_value = dist_matrix[i][j]
  #cnt += 1
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = max_value + 1
    queue.append([i-1,j])
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = max_value + 1
    queue.append([i+1,j])
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = max_value + 1
    queue.append([i,j-1])
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = max_value + 1
    queue.append([i,j+1])

#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

H, W = map(int, input().split())
dist_matrix = [[-1] * W for i in range(H)]
#queue = []
queue = deque()
for i in range(H):
  line_list = list(input())
  for j,ch in enumerate(line_list):
    if ch == "#":
      dist_matrix[i][j] = 0
      queue.append([i,j])

#cnt = 0
#print(queue)
max_value = 0
#while(True):
for c in range(100000000):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  i,j = queue.popleft()
  max_value = dist_matrix[i][j]
  #cnt += 1
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = max_value + 1
    queue.append([i-1,j])
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = max_value + 1
    queue.append([i+1,j])
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = max_value + 1
    queue.append([i,j-1])
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = max_value + 1
    queue.append([i,j+1])

#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

H, W = map(int, input().split())
dist_matrix = [[-1] * W for i in range(H)]
#queue = []
queue = deque()
for i in range(H):
  line_list = list(input())
  #for j in range(W):
  for j,ch in enumerate(line_list):
    #if line_list[j] == "#":  
    if ch == "#":
      dist_matrix[i][j] = 0
      queue.append([i,j])

#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  #i,j = queue.pop(0)
  i,j = queue.popleft()
  max_value = dist_matrix[i][j]
  #cnt += 1
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = max_value + 1
    queue.append([i-1,j])
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = max_value + 1
    queue.append([i+1,j])
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = max_value + 1
    queue.append([i,j-1])
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = max_value + 1
    queue.append([i,j+1])

#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
from collections import deque

H, W = map(int, input().split())
dist_matrix = [[-1] * W for i in range(H)]
#queue = []
queue = deque()
for i in range(H):
  line_list = list(input())
  for j in range(W):
    if line_list[j] == "#":  
      dist_matrix[i][j] = 0
      queue.append([i,j])

#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  #i,j = queue.pop(0)
  i,j = queue.popleft()
  max_value = dist_matrix[i][j]
  #cnt += 1
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = max_value + 1
    queue.append([i-1,j])
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = max_value + 1
    queue.append([i+1,j])
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = max_value + 1
    queue.append([i,j-1])
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = max_value + 1
    queue.append([i,j+1])

#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
dist_matrix = [[-1] * W for i in range(H)]
queue = []
for i in range(H):
  line_list = list(input())
  black_index_list = [i for i, x in enumerate(line_list) if x == '#']
  for j in black_index_list:
    dist_matrix[i][j] = 0
    queue.append([i,j])
  #for j in range(W):
  #  if line_list[j] == "#":  
  #    dist_matrix[i][j] = 0
  #    queue.append([i,j])

#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  i,j = queue.pop(0)
  max_value = dist_matrix[i][j]
  #cnt += 1
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = max_value + 1
    queue.append([i-1,j])
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = max_value + 1
    queue.append([i+1,j])
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = max_value + 1
    queue.append([i,j-1])
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = max_value + 1
    queue.append([i,j+1])

#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
dist_matrix = [[-1] * W for i in range(H)]
queue = []
for i in range(H):
  line_list = list(input())
  for j in range(W):
    if line_list[j] == "#":  
      dist_matrix[i][j] = 0
      queue.append([i,j])

#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  i,j = queue.pop(0)
  max_value = dist_matrix[i][j]
  #cnt += 1
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = max_value + 1
    queue.append([i-1,j])
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = max_value + 1
    queue.append([i+1,j])
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = max_value + 1
    queue.append([i,j-1])
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = max_value + 1
    queue.append([i,j+1])

#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
dist_matrix = [[-1] * W for i in range(H)]
queue = []
for i in range(H):
  line_list = list(input())
  for j in range(W):
    if line_list[j] == "#":  
      dist_matrix[i][j] = 0
      queue.append([i,j])

#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  i,j = queue.pop(0)
  max_value = dist_matrix[i][j]
  #cnt += 1
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = dist_matrix[i][j] + 1
    queue.append([i-1,j])
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = dist_matrix[i][j] + 1
    queue.append([i+1,j])
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = dist_matrix[i][j] + 1
    queue.append([i,j-1])
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = dist_matrix[i][j] + 1
    queue.append([i,j+1])

#print(cnt)
#print(dist_matrix)
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
H, W = map(int, input().split())
dist_matrix = [[-1] * W for i in range(H)]
queue = []
for i in range(H):
  line_list = list(input())
  for j in range(W):
    if line_list[j] == "#":  
      dist_matrix[i][j] = 0
      queue.append([i,j])
 
#print(queue)
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  i,j = queue.pop(0)
  if i > 0 and dist_matrix[i-1][j] == -1:
    dist_matrix[i-1][j] = dist_matrix[i][j] + 1
    queue.append([i-1,j])
  if i < H-1 and dist_matrix[i+1][j] == -1:
    dist_matrix[i+1][j] = dist_matrix[i][j] + 1
    queue.append([i+1,j])
  if j > 0 and dist_matrix[i][j-1] == -1:
    dist_matrix[i][j-1] = dist_matrix[i][j] + 1
    queue.append([i,j-1])
  if j < W-1 and dist_matrix[i][j+1] == -1:
    dist_matrix[i][j+1] = dist_matrix[i][j] + 1
    queue.append([i,j+1])
  
#print(dist_matrix)
max_value = 0
for i in range(H):
  for j in range(W):
    if dist_matrix[i][j] > max_value:
      max_value = dist_matrix[i][j]
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
#import copy
import sys
 
H, W = map(int, input().split())
#dist_matrix = [[10000] * W for i in range(H)]
black_h_list = []
black_w_list = []
for i in range(H):
  line_list = list(input())
  for j in range(W):
    if line_list[j] == "#":  
      black_h_list.append(i)
      black_w_list.append(j)
 
#print(black_h_list)
#print(black_w_list)

if len(black_h_list) == H*W:
  print(0)
  sys.exit()
  
max_value = 1
for i in range(H):
  for j in range(W):
    min_dist = H+W+2
    if j > 0:
      min_dist = last_dist+1
      
    for k in range(len(black_h_list)):
      if i-black_h_list[k] >= min_dist:
        continue
      elif black_h_list[k]-i >= min_dist:
        break      
      if j-black_w_list[k] >= min_dist:
        continue
      elif black_w_list[k]-j >= min_dist:
        continue
      
      dist = abs(i-black_h_list[k]) + abs(j-black_w_list[k])
      if max_value >= dist:
        min_dist = dist
        break
      elif min_dist > dist:
        min_dist = dist        
    #dist_matrix[i][j] = min_dist
    if max_value < min_dist:
      max_value = min_dist
      
    last_dist = min_dist
    #print(str(i) + "," + str(j) + "," + str(min_dist))

#print(dist_matrix)
    
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
#import copy
import sys
 
H, W = map(int, input().split())
#dist_matrix = [[10000] * W for i in range(H)]
black_h_list = []
black_w_list = []
for i in range(H):
  line_list = list(input())
  for j in range(W):
    if line_list[j] == "#":  
      black_h_list.append(i)
      black_w_list.append(j)
 
#print(black_h_list)
#print(black_w_list)

if len(black_h_list) == H*W:
  print(0)
  sys.exit()
  
max_value = 1
for i in range(H):
  for j in range(W):
    min_dist = H+W+2
    if j > 0:
      min_dist = last_dist+1
      
    for k in range(len(black_h_list)):
      if i-black_h_list[k] >= min_dist:
        continue
      elif black_h_list[k]-i >= min_dist:
        break
      
      dist = abs(i-black_h_list[k]) + abs(j-black_w_list[k])
      if max_value >= dist:
        min_dist = dist
        break
      elif min_dist > dist:
        min_dist = dist        
    #dist_matrix[i][j] = min_dist
    if max_value < min_dist:
      max_value = min_dist
      
    last_dist = min_dist
    #print(str(i) + "," + str(j) + "," + str(min_dist))

#print(dist_matrix)
    
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
import copy

H, W = map(int, input().split())
#dist_matrix = [[10000] * W for i in range(H)]
black_h_list = []
black_w_list = []
for i in range(H):
  line_list = list(input())
  for j in range(W):
    if line_list[j] == "#":  
      black_h_list.append(i)
      black_w_list.append(j)

#print(black_h_list)
#print(black_w_list)

max_value = 0
for i in range(H):
  for j in range(W):
    min_dist = H+W+2
    for k in range(len(black_h_list)):
      dist = abs(i-black_h_list[k]) + abs(j-black_w_list[k])
      if max_value >= dist:
        min_dist = dist
        break
      elif min_dist > dist:
        min_dist = dist        
    #dist_matrix[i][j] = min_dist
    if max_value < min_dist:
      max_value = min_dist

#print(dist_matrix)
    
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Time Limit Exceeded):
import copy

H, W = map(int, input().split())
dist_matrix = [[10000] * W for i in range(H)]
black_h_list = []
black_w_list = []
for i in range(H):
  line_list = list(input())
  for j in range(W):
    if line_list[j] == "#":  
      black_h_list.append(i)
      black_w_list.append(j)

#print(black_h_list)
#print(black_w_list)

for i in range(H):
  for j in range(W):
    min_dist = H+W+2
    for k in range(len(black_h_list)):
      dist = abs(i-black_h_list[k]) + abs(j-black_w_list[k])
      if min_dist > dist:
        min_dist = dist
    dist_matrix[i][j] = min_dist

#print(dist_matrix)
    
max_value = 0
for i in range(H):
  for j in range(W):
    if max_value < dist_matrix[i][j]:
      max_value = dist_matrix[i][j]
      
print(max_value)

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)

Buggy python submission (verdict: Runtime Error):
import copy

H, W = map(int, input().split())
matrix = [[0] * W for i in range(H)]
for i in range(H):
  line_list = list(input())
  for j in range(W):
    if line_list[j] == ".":  
      matrix[i][j] = 0
    else:
      matrix[i][j] = 1
      
cnt = 0
while(True):
  
  flg = True
  for i in range(H):
    for j in range(W):
      if matrix[i][j] == 0:
        flg = False
        break
  
  if flg:
    print(cnt)
    break
  
  matrix_copy = copy.deepcopy(matrix)
  cnt += 1
  for i in range(H):
    for j in range(W):
      if matrix[i][j] == 1:
        if i > 0:
          matrix_copy[i-1][j] = 1
        if i < H-1:
          matrix_copy[i+1][j] = 1
        if j > 0:
          matrix_copy[i][j-1] = 1
        if j < H-1:
          matrix_copy[i][j+1] = 1
   
  matrix = matrix_copy

Fixed submission:
from collections import deque
import sys
input = sys.stdin.readline
 
H, W = map(int, input().split())
mark_matrix = [[True]*(W+2)]
#mark_matrix.extend([[True]+[False]*(W)+[True] for _ in range(H)])
mark_matrix.extend([[True]+[x!='.' for x in input()] for _ in range(H)])
mark_matrix[H].append(True)
mark_matrix.append([True]*(W+2))
#queue = []
queue = deque()
for i in range(1,H+1):
  for j in range(1,W+1):
    if mark_matrix[i][j]:
      queue.append((i,j))
#  line = input()
#  for j,ch in enumerate(line):
#    if ch == "#":
#      mark_matrix[i+1][j+1] = True
#      queue.append((i+1,j+1))
#for i in range(1,H+1):
#  mark_matrix[i][0] = True
#  mark_matrix[i][W+1] = True
#for j in range(W+2):
#  mark_matrix[0][j] = True
#  mark_matrix[H+1][j] = True
#print(mark_matrix)
 
#cnt = 0
#print(queue)
max_value = 0
while(True):
  #print(len(queue))
  if len(queue) == 0:
    break
  
  new_queue = deque()
  for i,j in queue:
  
    if not mark_matrix[i-1][j]:
      mark_matrix[i-1][j] = True
      #queue.append((i-1,j))
      new_queue.append((i-1,j))
    if not mark_matrix[i+1][j]:
      mark_matrix[i+1][j] = True
      #queue.append((i+1,j))
      new_queue.append((i+1,j))
    if not mark_matrix[i][j-1]:
      mark_matrix[i][j-1] = True
      #queue.append((i,j-1))
      new_queue.append((i,j-1))
    if not mark_matrix[i][j+1]:
      mark_matrix[i][j+1] = True
      #queue.append((i,j+1))
      new_queue.append((i,j+1))
 
  if len(new_queue) == 0:
    break
  else:
    queue = new_queue
    max_value += 1
  
#print(cnt)
#print(dist_matrix)
print(max_value)