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

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append(["#" * W])
for h in range(H-2):
  grid.append(["#" + input() + "#"])
grid.append(["#" * W])

INF = 10**9
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    m_grid = 0
    if grid[h][0][w]=="#": continue

    dist = [[INF]*W for i in range(H)]
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      m_grid = max(d_v, m_grid)
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][0][n_w]=="#": continue
        d_n = d_v + 1
        if d_n > dist[n_h][n_w]:
          continue

        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))
        m_grid = max(d_n, m_grid)

    
    ans = max(ans, m_grid)

print(ans)

      


    


Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)

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

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append(["#" * W])
for h in range(H-2):
  grid.append(["#" + input() + "#"])
grid.append(["#" * W])

INF = 10**9
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    
    if grid[h][0][w]=="#": continue

    dist = [[INF]*W for i in range(H)]
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][0][n_w]=="#": continue
        d_n = d_v + 1
        if d_n > dist[n_h][n_w]:
          continue
        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))

    new_dist =[]
    for l in dist:
      new_dist.append([x for x in l if x < INF])
    LL = [max(l) if len(l)>0 else 0 for l in new_dist]
    ans = max(ans, max(LL))

print(ans)

      


    


Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)

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

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append(["#" * W])
for h in range(H-2):
  grid.append(["#" + input() + "#"])
grid.append(["#" * W])

INF = 10**9
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    
    if grid[h][0][w]=="#": continue

    dist = [[INF]*W for i in range(H)]
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][0][n_w]=="#": continue
        d_n = d_v + 1
        if d_n > dist[n_h][n_w]:
          continue
        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))

    new_dist =[]
    for l in dist:
      new_dist.append([x for x in l if x < INF])
    LL = [max(l) if len(l)>0 else 0 for l in new_dist]
    ans = max(ans, max(LL))

print(ans)

Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)

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

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append("#" * W)
for h in range(H-2):
  grid.append("#" + input() + "#")
grid.append("#" * W)

INF = 10**9
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    
    if grid[h][w]=="#": continue

    dist = np.array([[INF]*W for i in range(H)])
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][n_w]=="#": continue
        d_v = dist[v_h][v_w]
        d_n = d_v + 1
        if (dist[n_h][n_w] == -1) & (d_n > dist[n_h][n_w]):
          continue
        
        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))


    
      dist_m = max(x for x in dist.flatten() if x < INF)
      ans = max(ans, dist_m)

print(ans)

      


    

Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
import numpy as np

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append("#" * W)
for h in range(H-2):
  grid.append("#" + input() + "#")
grid.append("#" * W)

INF = -1
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    
    if grid[h][w]=="#": continue

    dist = np.array([[INF]*W for i in range(H)])
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][n_w]=="#": continue
        d_v = dist[v_h][v_w]
        d_n = d_v + 1
        if (dist[n_h][n_w] == -1) & (d_n > dist[n_h][n_w]):
          continue
        
        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))


    
      dist_m = max(x for x in dist.flatten() if x < INF)
      ans = max(ans, dist_m)

print(ans)

      


    

Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
#import numpy as np

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append("#" * W)
for h in range(H-2):
  grid.append("#" + input() + "#")
grid.append("#" * W)

INF = -1
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    
    if grid[h][w]=="#": continue

    dist = np.array([[INF]*W for i in range(H)])
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][n_w]=="#": continue
        d_v = dist[v_h][v_w]
        d_n = d_v + 1
        if (dist[n_h][n_w] == -1) & (d_n > dist[n_h][n_w]):
          continue
        
        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))


    
      dist_m = max(x for x in dist.flatten() if x < INF)
      ans = max(ans, dist_m)

print(ans)

      


    

Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)

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

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append("#" * W)
for h in range(H-2):
  grid.append("#" + input() + "#")
grid.append("#" * W)

INF = 10**9
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    
    if grid[h][w]=="#": continue

    dist = np.array([[INF]*W for i in range(H)])
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][n_w]=="#": continue
        d_n = d_v + 1
        if d_n > dist[n_h][n_w]:
          continue
        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))


    
      dist_m = max(x for x in dist.flatten() if x < INF)
      ans = max(ans, dist_m)

print(ans)

      


    

Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)

Buggy python submission (verdict: Runtime Error):
from collections import deque
import numpy as np

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append("#" * W)
for h in range(H-2):
  grid.append("#" + input() + "#")
grid.append("#" * W)

INF = 10**9
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    
    if grid[h][w]=="#": continue

    dist = np.array([[INF]*W for i in range(H)])
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][n_w]=="#": continue
        d_n = d_v + 1
        if d_n > dist[n_h][n_w]:
          continue
        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))


    
      dist_m = max(x for x in dist.flatten() if x < INF)
      ans = max(ans, dist_m)

print(ans)

      


    

Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)

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

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append(["#" * W])
for h in range(H-2):
  grid.append(["#" + input() + "#"])
grid.append(["#" * W])

INF = 10**9
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    
    if grid[h][0][w]=="#": continue

    dist = [[INF]*W for i in range(H)]
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][0][n_w]=="#": continue
        d_n = d_v + 1
        if d_n > dist[n_h][n_w]:
          continue
        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))

      new_dist =[]
      for l in dist:
        new_dist.append([x for x in l if x < INF])
      #print(new_dist)
      LL = [max(l) if len(l)>0 else 0 for l in new_dist]
      #print(LL)
      ans = max(ans, max(LL))

print(ans)

      


    

Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)

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

H, W = map(int, input().split())
H += 2; W += 2
grid = []
grid.append(["#" * W])
for h in range(H-2):
  grid.append(["#" + input() + "#"])
grid.append(["#" * W])

INF = 10**9
ans = 0
for h in range(1, H-1):
  for w in range(1, W-1):
    
    if grid[h][0][w]=="#": continue

    dist = [[INF]*W for i in range(H)]
    dist[h][w] = 0 
    q = deque([(h,w)])

    while(q):
      v_h, v_w = q.popleft()
      d_v = dist[v_h][v_w]
      for n_h, n_w in ((v_h, v_w-1),(v_h, v_w+1),(v_h-1, v_w),(v_h+1, v_w)):
        if grid[n_h][0][n_w]=="#": continue
        d_n = d_v + 1
        if d_n > dist[n_h][n_w]:
          continue
        dist[n_h][n_w] = d_n
        q.append((n_h,n_w))

      new_dist =[]
      for l in dist:
        new_dist.append([x for x in l if x < INF])
      #print(new_dist)
      LL = [max(l) if len(l)>0 else 0 for l in new_dist]
      #print(LL)
      ans = max(ans, max(LL))

print(ans)

      


    

Fixed submission:
from collections import deque
import numpy as np

H,W = map(int,input().split())
maze = [input() for _ in range(H)]

ans = 0
for x in range(H):
    for y in range(W):
        #壁からはスタートできない
        if maze[x][y] == "#":
            continue

        #初期化
        distance = [[0]*W for _ in range(H)]
        #start位置
        stack = deque([[x,y]])

        while stack:
            h,w = stack.popleft()
            for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
                new_h, new_w = h+i, w+j
                if new_h < 0 or new_w < 0 or new_h >= H or new_w >= W:
                    continue
                elif maze[new_h][new_w] != "#" and distance[new_h][new_w] == 0:
                    distance[new_h][new_w] = distance[h][w]+1
                    stack.append([new_h, new_w])

        #start位置は0で初期化
        distance[x][y] = 0
        ans = max(ans, np.max(distance))

print(ans)