Buggy python submission (verdict: Runtime Error):
from collections import deque
 
h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]
 
dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
ans = 0
for i in range(h):
    for j in range(w):
        if s[i][j] == '#': continue
        q = deque()
        q.append((i, j, 0))
        visited = [[False] * w for _ in range(h)]
        while q:
            x, y, z = q.popleft()
            for dx, dy in dirr:
                nx, ny = x + dx, y + dy
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx, ny] and s[nx][ny] == '.':
                        q.append((nx, ny, z + 1))
                        if z + 1 > ans: ans = z + 1
                        visited[nx][ny] = True
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from collections import deque
 
h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]
 
dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
visited = np.zeros((h, w))
ans = 0
for i in range(h):
    for j in range(w):
        if s[i][j] == '#': continue
        q = deque()
        q.append((i, j, 0))
        visited[:, :] = 0
        while q:
            x, y, z = q.popleft()
            for dx, dy in dirr:
                nx, ny = x + dx, y + dy
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx, ny] and s[nx][ny] == '.':
                        q.append((nx, ny, z + 1))
                        if z + 1 > ans: ans = z + 1
                        visited[x, y] = 1
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

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

h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]

ans = 0
for i in range(h):
    for j in range(w):
        if s[i][j] == '#': continue
        q = deque()
        q.append([i, j, 0])
        visited = np.zeros((h + 5, w + 5), dtype = bool)
        dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
        mx = 0
        while len(q) != 0:
            x, y, z = q[0]
            for p in range(4):
                nx, ny = x + dirr[p][0], y + dirr[p][1]
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx][ny] and s[nx][ny] == '.':
                        q.append([nx, ny, z + 1])
                        visited[x][y] = True
                        ans = max(ans, z + 1)
            q.popleft()
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from collections import deque
 
h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]
 
dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
visited = np.zeros((h, w))
ans = 0
for i in range(h):
    for j in range(w):
        if s[i][j] == '#': continue
        q = deque()
        q.append((i, j, 0))
        visited[:, :] = 0
        while q:
            x, y, z = q.popleft()
            if z > ans: ans = z
            visited[x, y] = 1
            for dx, dy in dirr:
                nx, ny = x + dx, y + dy
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx, ny] and s[nx][ny] == '.':
                        q.append((nx, ny, z + 1))
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from collections import deque
 
h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]
 
dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
visited = np.zeros((h, w))
ans = 0
for i in range(h):
    for j in range(w):
        if s[i][j] == '#': continue
        q = deque()
        q.append([i, j, 0])
        visited[:, :] = 0
        while q:
            x, y, z = q.popleft()
            if z > ans: ans = z
            visited[x, y] = 1
            for dx, dy in dirr:
                nx, ny = x + dx, y + dy
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx, ny] and s[nx][ny] == '.':
                        q.append([nx, ny, z + 1])
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from collections import deque
 
h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]
 
dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
visited = np.zeros((h + 5, w + 5))
ans = 0
for i in range(h):
    for j in range(w):
        q = deque()
        q.append([i, j, 0])
        if s[i][j] == '#': continue
        visited[:, :] = 0
        while q:
            x, y, z = q.popleft()
            if z > ans: ans = z
            visited[x][y] = True
            for dx, dy in dirr:
                nx, ny = x + dx, y + dy
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx][ny] and s[nx][ny] == '.':
                        q.append([nx, ny, z + 1])
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from collections import deque
 
h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]
 
dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
ans = 0
for i in range(h):
    for j in range(w):
        q = deque()
        q.append([i, j, 0])
        if s[i][j] == '#': continue
        visited = np.zeros((h + 5, w + 5))
        while q:
            x, y, z = q.popleft()
            if z > ans: ans = z
            visited[x][y] = True
            for dx, dy in dirr:
                nx, ny = x + dx, y + dy
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx][ny] and s[nx][ny] == '.':
                        q.append([nx, ny, z + 1])
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

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

h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]

ans = 0
for i in range(h):
    for j in range(w):
        if s[i][j] == '#': continue
        q = deque()
        q.append([i, j, 0])
        visited = np.zeros((h + 5, w + 5), dtype = bool)
        dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
        mx = 0
        while len(q) != 0:
            x, y, z = q[0]
            ans = max(ans, z)
            visited[x][y] = True
            for p in range(4):
                nx, ny = x + dirr[p][0], y + dirr[p][1]
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx][ny] and s[nx][ny] == '.':
                        q.append([nx, ny, z + 1])
            q.popleft()
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from collections import deque
 
h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]
 
dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
ans = 0
for i in range(h):
    for j in range(w):
        q = deque()
        q.append([i, j, 0])
        if s[i][j] == '#': continue
        visited = np.zeros((h + 5, w + 5))
        while q:
            x, y, z = q.popleft()
            if z > ans: ans = z
            visited[x][y] = True
            for p in range(4):
                nx, ny = x + dirr[p][0], y + dirr[p][1]
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx][ny] and s[nx][ny] == '.':
                        q.append([nx, ny, z + 1])
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from collections import deque
 
h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]
 
dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
ans = 0
for i in range(h):
    for j in range(w):
        q = deque()
        q.append([i, j, 0])
        if s[i][j] == '#': continue
        visited = np.zeros((h + 5, w + 5), dtype = bool)
        while q:
            x, y, z = q.popleft()
            if z > ans: ans = z
            visited[x][y] = True
            for p in range(4):
                nx, ny = x + dirr[p][0], y + dirr[p][1]
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx][ny] and s[nx][ny] == '.':
                        q.append([nx, ny, z + 1])
print(ans)


Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)

Buggy python submission (verdict: Time Limit Exceeded):
import numpy as np
from collections import deque
 
h, w = map(int, input().split())
s = [list(input()) for _ in range(h)]
 
ans = 0
for i in range(h):
    for j in range(w):
        q = deque()
        q.append([i, j, 0])
        if s[i][j] == '#': continue
 
        visited = np.zeros((h + 5, w + 5), dtype = bool)
        dirr = [[1, 0], [0, 1], [-1, 0], [0, -1]]
        mx = 0
        while len(q) != 0:
            x, y, z = q.popleft()
            ans = max(ans, z)
            visited[x][y] = True
            for p in range(4):
                nx, ny = x + dirr[p][0], y + dirr[p][1]
                if 0 <= nx < h and 0 <= ny < w:
                    if not visited[nx][ny] and s[nx][ny] == '.':
                        q.append([nx, ny, z + 1])
print(ans)

Fixed submission:
#!/usr/bin/env python3
import sys
sys.setrecursionlimit(10**5)
input = sys.stdin.readline
from collections import deque

h, w = [int(item) for item in input().split()]
field = []
field.append("#" * (w + 2))
for i in range(h):
    field.append("#" + input().rstrip() + "#")
field.append("#" * (w + 2))


ans = 0
for i in range(1, h+1):
    for j in range(1, w+1):
        if field[i][j] == "#":
            continue
        dist = [[-1] * (w + 2) for _ in range(h + 2)]
        dist[i][j] = 0
        dq = deque()
        dq.append((i, j, 0))
        while dq:
            x, y, d = dq.popleft()
            if field[x+1][y] == "." and dist[x+1][y] == -1:
                dist[x+1][y] = d+1
                dq.append((x+1, y, d+1))
            if field[x][y+1] == "." and dist[x][y+1] == -1:
                dist[x][y+1] = d+1
                dq.append((x, y+1, d+1))
            if field[x-1][y] == "." and dist[x-1][y] == -1:
                dist[x-1][y] = d+1
                dq.append((x-1, y, d+1))
            if field[x][y-1] == "." and dist[x][y-1] == -1:
                dist[x][y-1] = d+1
                dq.append((x, y-1, d+1))
        for line in dist:
            ans = max(ans, max(line))
        
print(ans)