Problem: Takahashi has a maze, which is a grid of H \times W squares with H horizontal rows and W vertical columns.  The square at the i-th row from the top and the j-th column is a "wall" square if S_{ij} is `#`, and a "road" square if S_{ij} is `.`.  From a road square, you can move to a horizontally or vertically adjacent road square.  You cannot move out of the maze, move to a wall square, or move diagonally.  Takahashi will choose a starting square and a goal square, which can be any road squares, and give the maze to Aoki.  Aoki will then travel from the starting square to the goal square, in the minimum number of moves required.  In this situation, find the maximum possible number of moves Aoki has to make.

Submission attempts (in order):
import math 
import bisect
import heapq
from collections import deque

h,w = map(int,input().split())
s = [map(int,input().split()) for _ in range(h)]
v = [ [0] * w ] * h

def bfs(i,j,s,v):
    count = 0
    mx = 0
    if s[i][j] == '#': return 0
    else:
        v[i][j] = 1
        if i+1 < h and j+1 < w :
            if v[i+1][j+1] != 1 and s[i+1][j+1] == '.':
                count += 1
                mx = max(count,mx)
                bfs(i+1,j+1,s,v)

        elif i+1 < h and j-1 > 0 :
            if v[i+1][j-1] != 1 and s[i+1][j-1] == '.':
                count += 1
                mx = max(count,mx)
                bfs(i+1,j-1,s,v)

        elif i-1 < h and j+1 > 0 :
            if v[i-1][j+1] != 1 and s[i-1][j+1] == '.':
                count += 1
                mx = max(count,mx)
                bfs(i-1,j+1,s,v)

        elif i-1 < h and j-1 > 0 :
            if v[i+1][j-1] != 1 and s[i-1][j-1] == '.':
                count += 1
                mx = max(count,mx)
                bfs(i-1,j-1,s,v)


    return mx

ans = 1000000
for i in range(h):
    for j in range(w):
        x,y = i,j
        ans = min(ans,bfs(i,j,s,v))
        

import math 
import bisect
import heapq
from collections import deque

h,w = map(int,input().split())
s = [map(int,input().split()) for _ in range(h)]
v = [ [0] * w ] * h

def bfs(i,j,s,v,count):

    if s[i][j] == '#': return 0
    else:
        v[i][j] = 1
        if i+1 < h and j+1 < w :
            if v[i+1][j+1] != 1 and s[i+1][j+1] == '.':
                count += 1
                bfs(i+1,j+1,s,v,count)

        elif i+1 < h and j-1 > 0 :
            if v[i+1][j-1] != 1 and s[i+1][j-1] == '.':
                count += 1
     
                bfs(i+1,j-1,s,v,count)

        elif i-1 < h and j+1 > 0 :
            if v[i-1][j+1] != 1 and s[i-1][j+1] == '.':
                count += 1
       
                bfs(i-1,j+1,s,v,count)

        elif i-1 < h and j-1 > 0 :
            if v[i+1][j-1] != 1 and s[i-1][j-1] == '.':
                count += 1
               
                bfs(i-1,j-1,s,v,count)

        else :return count

ans = 1000000
for i in range(h):
    for j in range(w):
        x,y = i,j
        ans = min(ans,bfs(i,j,s,v))
        

import math 
import bisect
import heapq
from collections import deque

h,w = map(int,input().split())
s = [map(int,input().split()) for _ in range(h)]
v = [ [0] * w ] * h

def bfs(i,j,s,v,count):

    if s[i][j] == '#': return 0
    else:
        v[i][j] = 1
        if i+1 < h and j+1 < w :
            if v[i+1][j+1] != 1 and s[i+1][j+1] == '.':
                count += 1
                bfs(i+1,j+1,s,v,count)

        elif i+1 < h and j-1 > 0 :
            if v[i+1][j-1] != 1 and s[i+1][j-1] == '.':
                count += 1
     
                bfs(i+1,j-1,s,v,count)

        elif i-1 < h and j+1 > 0 :
            if v[i-1][j+1] != 1 and s[i-1][j+1] == '.':
                count += 1
       
                bfs(i-1,j+1,s,v,count)

        elif i-1 < h and j-1 > 0 :
            if v[i+1][j-1] != 1 and s[i-1][j-1] == '.':
                count += 1
               
                bfs(i-1,j-1,s,v,count)

        else :return count

ans = 0
for i in range(h):
    for j in range(w):
        x,y = i,j
        ans = max(ans,bfs(i,j,s,v,0))

print(ans)

import math 
import bisect
import heapq
from collections import deque

h,w = map(int,input().split())
s = [map(int,input().split()) for _ in range(h)]
v = [ [0] * w ] * h

bfs(i,j,s,v):
    count = 0
    mx = 0
    if s[i][j] == '#': return 0
    elif:
        v[i][j] = 1
        if i+1 < h and j+1 < w 
            if v[i+1][j+1] != 1 and s[i+1][j+1] == '.'
                count += 1
                mx = max(count,mx)
                bfs(i+1,j+1,s,v)

        elif i+1 < h and j-1 > 0 
            if v[i+1][j-1] != 1 and s[i+1][j-1] == '.'
                count += 1
                mx = max(count,mx)
                bfs(i+1,j-1,s,v)

        elif i-1 < h and j+1 > 0 
            if v[i-1][j+1] != 1 and s[i-1][j+1] == '.'
                count += 1
                mx = max(count,mx)
                bfs(i-1,j+1,s,v)

        elif i-1 < h and j-1 > 0 
            if v[i+1][j-1] != 1 and s[i-1][j-1] == '.'
                count += 1
                mx = max(count,mx)
                bfs(i-1,j-1,s,v)


    return mx

ans = 1000000
for i in range(h):
    for j in range(w):
        x,y = i,j
        ans = min(ans,bfs(i,j,s,v))
        

import math 
import bisect
import heapq
from collections import deque

h,w = map(int,input().split())
s = [map(int,input().split()) for _ in range(h)]
v = [ [0] * w ] * h

def bfs(i,j,s,v,count):

    if s[i][j] == '#': return 0
    else:
        v[i][j] = 1
        if i+1 < h and j+1 < w :
            if v[i+1][j+1] != 1 and s[i+1][j+1] == '.':
                count += 1
                bfs(i+1,j+1,s,v,count)

        elif i+1 < h and j-1 > 0 :
            if v[i+1][j-1] != 1 and s[i+1][j-1] == '.':
                count += 1
     
                bfs(i+1,j-1,s,v,count)

        elif i-1 < h and j+1 > 0 :
            if v[i-1][j+1] != 1 and s[i-1][j+1] == '.':
                count += 1
       
                bfs(i-1,j+1,s,v,count)

        elif i-1 < h and j-1 > 0 :
            if v[i+1][j-1] != 1 and s[i-1][j-1] == '.':
                count += 1
               
                bfs(i-1,j-1,s,v,count)

        else :return count

ans = 1000000
for i in range(h):
    for j in range(w):
        x,y = i,j
        ans = min(ans,bfs(i,j,s,v,0))
        

import math 
import bisect
import heapq
from collections import deque

h,w=map(int,input().split())
M=[]
M=[input() for _ in range(h)]
 
def bfs(x,y):
    dist=[[-1]*w  for _ in range(h)]
    seen=[[False]*w for _ in range(h)]
    stk=[(x,y,0)]
    while stk:
        px,py,dst=stk.pop(0)
        if seen[px][py]:
            continue
        seen[px][py]=True
        
        if M[px][py]=='#':
            dist[px][py]=0
            continue
        
        for x,y in [(-1,0),(1,0),(0,-1),(0,1)]:
            if px+x<0 or px+x>=h or py+y<0 or py+y>=w:
                continue
            else:
                stk.append((px+x,py+y,dst+1))
        dist[px][py]=dst
    ans=0
 
    for i in range(h):
        ans=max(max(dist[i]),ans)
    return ans
ans = 0
for i in range(h):
    for j in range(w):
        if M[i][j]=='#':
            continue
        ans=max(bfs(i,j),ans)
print(ans)

Verdicts: Runtime Error

Runtime Error

Runtime Error

Runtime Error

Runtime Error

Accepted