Problem:
 Score : 400 points    Problem Statement 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.      Constraints  1 \leq H,W \leq 20  S_{ij} is . or # .  S contains at least two occurrences of . .  Any road square can be reached from any road square in zero or more moves.         Input Input is given from Standard Input in the following format:  H  W  S_{11} ... S_{1W}  :  S_{H1} ... S_{HW}       Output Print the maximum possible number of moves Aoki has to make.        Sample Input 1 3 3
...
...
...      Sample Output 1 4  If Takahashi chooses the top-left square as the starting square and the bottom-right square as the goal square, Aoki has to make four moves.       Sample Input 2 3 5
...#.
.#.#.
.#...      Sample Output 2 10  If Takahashi chooses the bottom-left square as the starting square and the top-right square as the goal square, Aoki has to make ten moves.

Solution (Python):
import copy

def maze_maker():
    h,w = map(int,input().split())
    maze = []
    for i in range(h):
        maze.append(list(input()))
    return maze,h,w

def search():
    v = 0
    now = [[i1,j1,0]]
    meiro[i1][j1] = 0
    go = True
    while go:
        for i in now[:]:
            
            if i[0] == 0:
                pass
            else:
                if meiro[i[0]-1][i[1]] == ".":
                    now.append([i[0]-1,i[1],i[2]+1])
                    meiro[i[0]-1][i[1]] = i[2]+1
            
            if i[0] == h-1:
                pass
            else:
                if meiro[i[0]+1][i[1]] == ".":
                    now.append([i[0]+1,i[1],i[2]+1])
                    meiro[i[0]+1][i[1]] = i[2]+1
            
            if i[1] == 0:
                pass
            else:
                if meiro[i[0]][i[1]-1] == ".":
                    now.append([i[0],i[1]-1,i[2]+1])
                    meiro[i[0]][i[1]-1] = i[2]+1
            
            if i[1] == w-1:
                pass
            else:
                if meiro[i[0]][i[1]+1] == ".":
                    now.append([i[0],i[1]+1,i[2]+1])
                    meiro[i[0]][i[1]+1] = i[2]+1
            v = max(v,i[2])
            now.remove(i)
            if now == []:
                return v


saitankeiro = 0
maze,h,w = maze_maker()
for i1 in range(h):
    for j1 in range(w):
        if maze[i1][j1] != "
            meiro = copy.deepcopy(maze)
            saitankeiro = max(saitankeiro,search())
print(saitankeiro)

Solution (Python):


import itertools


def main():
  H, W = map(int, input().split())
  M = list(itertools.chain.from_iterable([[c == '.' for c in input().strip()] for _ in range(H)]))
  size = W * H
  dist = [[size] * (size) for _ in range(size)]

  for i in range(size):
    if not M[i]:
      continue

    x, y = i % W, i // W

    dist[i][i] = 0

    if x > 0 and M[i - 1]:
      dist[i][i - 1] = 1
      dist[i - 1][i] = 1

    if y > 0 and M[i - W]:
      dist[i][i - W] = 1
      dist[i - W][i] = 1

  for i in range(size):
    for j in range(size):
      for k in range(size):
        if M[j] and M[k]:
          dist[j][k] = min(dist[j][k], dist[j][i] + dist[i][k])

  r = 1

  for v in itertools.chain.from_iterable(dist):
    if v < size:
      r = max(r, v)

  print(r)


if __name__ == '__main__':
  main()

Solution (Python):
from sys import stdin
import queue

H, W = [int(x) for x in stdin.readline().rstrip().split()]
maze = [stdin.readline().rstrip().split()[0] for _ in range(H)]

ans = 0

for h in range(H):
    for w in range(W):
        if maze[h][w] == '
            continue
        else:
            q = queue.Queue()
            q.put((h, w, 0))
            temp_h = h
            temp_w = w
            visited = [[0] * W for _ in range(H)]
            visited[h][w] = 1
            while q.qsize() > 0:
                temp = q.get()
                temp_h = temp[0]
                temp_w = temp[1]
                temp_d = temp[2]
                ans = max(ans, temp_d)
                if temp_h + 1 < H and maze[temp_h + 1][temp_w] == '.' and visited[temp_h + 1][temp_w] == 0:
                    visited[temp_h + 1][temp_w] = 1
                    q.put((temp_h + 1, temp_w, temp_d + 1))
                if temp_h - 1 >= 0 and maze[temp_h - 1][temp_w] == '.' and visited[temp_h - 1][temp_w] == 0:
                    visited[temp_h - 1][temp_w] = 1
                    q.put((temp_h - 1, temp_w, temp_d + 1))
                if temp_w + 1 < W and maze[temp_h][temp_w + 1] == '.' and visited[temp_h][temp_w + 1] == 0:
                    visited[temp_h][temp_w + 1] = 1
                    q.put((temp_h, temp_w + 1, temp_d + 1))
                if temp_w - 1 >= 0 and maze[temp_h][temp_w - 1] == '.' and visited[temp_h][temp_w - 1] == 0:
                    visited[temp_h][temp_w - 1] = 1
                    q.put((temp_h, temp_w - 1, temp_d + 1))

print(ans)

Solution (Python):
from sys import stdin
import queue

H, W = [int(x) for x in stdin.readline().rstrip().split()]
maze = [stdin.readline().rstrip().split()[0] for _ in range(H)]

ans = 0

for h in range(H):
    for w in range(W):
        if maze[h][w] == '
            continue
        else:
            q = queue.Queue()
            q.put((h, w, 0))
            temp_h = h
            temp_w = w
            visited = [[0] * W for _ in range(H)]
            visited[h][w] = 1
            while q.qsize() > 0:
                temp = q.get()
                temp_h = temp[0]
                temp_w = temp[1]
                temp_d = temp[2]
                ans = max(ans, temp_d)
                if temp_h + 1 < H and maze[temp_h + 1][temp_w] == '.' and visited[temp_h + 1][temp_w] == 0:
                    visited[temp_h + 1][temp_w] = visited[temp_h][temp_w] + 1
                    q.put((temp_h + 1, temp_w, temp_d + 1))
                if temp_h - 1 >= 0 and maze[temp_h - 1][temp_w] == '.' and visited[temp_h - 1][temp_w] == 0:
                    visited[temp_h - 1][temp_w] = visited[temp_h][temp_w] + 1
                    q.put((temp_h - 1, temp_w, temp_d + 1))
                if temp_w + 1 < W and maze[temp_h][temp_w + 1] == '.' and visited[temp_h][temp_w + 1] == 0:
                    visited[temp_h][temp_w + 1] = visited[temp_h][temp_w] + 1
                    q.put((temp_h, temp_w + 1, temp_d + 1))
                if temp_w - 1 >= 0 and maze[temp_h][temp_w - 1] == '.' and visited[temp_h][temp_w - 1] == 0:
                    visited[temp_h][temp_w - 1] = visited[temp_h][temp_w] + 1
                    q.put((temp_h, temp_w - 1, temp_d + 1))

print(ans)

Solution (Python):
from sys import stdin
import queue

H, W = [int(x) for x in stdin.readline().rstrip().split()]
maze = [stdin.readline().rstrip().split()[0] for _ in range(H)]

ans = 0

for h in range(H):
    for w in range(W):
        if maze[h][w] == '
            continue
        else:
            q = queue.Queue()
            q.put((h, w, 0))
            visited = [[0] * W for _ in range(H)]
            visited[h][w] = 1
            while q.qsize() > 0:
                temp = q.get()
                temp_h = temp[0]
                temp_w = temp[1]
                temp_d = temp[2]
                ans = max(ans, temp_d)
                if temp_h + 1 < H and maze[temp_h + 1][temp_w] == '.' and visited[temp_h + 1][temp_w] == 0:
                    visited[temp_h + 1][temp_w] = visited[temp_h][temp_w] + 1
                    q.put((temp_h + 1, temp_w, temp_d + 1))
                if temp_h - 1 >= 0 and maze[temp_h - 1][temp_w] == '.' and visited[temp_h - 1][temp_w] == 0:
                    visited[temp_h - 1][temp_w] = visited[temp_h][temp_w] + 1
                    q.put((temp_h - 1, temp_w, temp_d + 1))
                if temp_w + 1 < W and maze[temp_h][temp_w + 1] == '.' and visited[temp_h][temp_w + 1] == 0:
                    visited[temp_h][temp_w + 1] = visited[temp_h][temp_w] + 1
                    q.put((temp_h, temp_w + 1, temp_d + 1))
                if temp_w - 1 >= 0 and maze[temp_h][temp_w - 1] == '.' and visited[temp_h][temp_w - 1] == 0:
                    visited[temp_h][temp_w - 1] = visited[temp_h][temp_w] + 1
                    q.put((temp_h, temp_w - 1, temp_d + 1))

print(ans)

Solution (Python):
from sys import stdin
import queue

H, W = [int(x) for x in stdin.readline().rstrip().split()]
maze = [stdin.readline().rstrip().split()[0] for _ in range(H)]

ans = 0

for h in range(H):
    for w in range(W):
        if maze[h][w] == '
            continue
        else:
            q = queue.Queue()
            q.put((h, w, 0))
            visited = [[-1] * W for _ in range(H)]
            visited[h][w] = 0
            while q.qsize() > 0:
                temp = q.get()
                temp_h = temp[0]
                temp_w = temp[1]
                temp_d = temp[2]
                ans = max(ans, visited[temp_h][temp_w])
                if temp_h + 1 < H and maze[temp_h + 1][temp_w] == '.' and visited[temp_h + 1][temp_w] < 0:
                    visited[temp_h + 1][temp_w] = visited[temp_h][temp_w] + 1
                    q.put((temp_h + 1, temp_w, temp_d + 1))
                if temp_h - 1 >= 0 and maze[temp_h - 1][temp_w] == '.' and visited[temp_h - 1][temp_w] < 0:
                    visited[temp_h - 1][temp_w] = visited[temp_h][temp_w] + 1
                    q.put((temp_h - 1, temp_w, temp_d + 1))
                if temp_w + 1 < W and maze[temp_h][temp_w + 1] == '.' and visited[temp_h][temp_w + 1] < 0:
                    visited[temp_h][temp_w + 1] = visited[temp_h][temp_w] + 1
                    q.put((temp_h, temp_w + 1, temp_d + 1))
                if temp_w - 1 >= 0 and maze[temp_h][temp_w - 1] == '.' and visited[temp_h][temp_w - 1] < 0:
                    visited[temp_h][temp_w - 1] = visited[temp_h][temp_w] + 1
                    q.put((temp_h, temp_w - 1, temp_d + 1))

print(ans)

Solution (Python):
from sys import stdin
import queue

H, W = [int(x) for x in stdin.readline().rstrip().split()]
maze = [stdin.readline().rstrip().split()[0] for _ in range(H)]

ans = 0

for h in range(H):
    for w in range(W):
        if maze[h][w] == '
            continue
        else:
            q = queue.Queue()
            q.put((h, w))
            visited = [[-1] * W for _ in range(H)]
            visited[h][w] = 0
            while q.qsize() > 0:
                temp = q.get()
                temp_h = temp[0]
                temp_w = temp[1]
                ans = max(ans, visited[temp_h][temp_w])
                if temp_h + 1 < H and maze[temp_h + 1][temp_w] == '.' and visited[temp_h + 1][temp_w] < 0:
                    visited[temp_h + 1][temp_w] = visited[temp_h][temp_w] + 1
                    q.put((temp_h + 1, temp_w))
                if temp_h - 1 >= 0 and maze[temp_h - 1][temp_w] == '.' and visited[temp_h - 1][temp_w] < 0:
                    visited[temp_h - 1][temp_w] = visited[temp_h][temp_w] + 1
                    q.put((temp_h - 1, temp_w))
                if temp_w + 1 < W and maze[temp_h][temp_w + 1] == '.' and visited[temp_h][temp_w + 1] < 0:
                    visited[temp_h][temp_w + 1] = visited[temp_h][temp_w] + 1
                    q.put((temp_h, temp_w + 1))
                if temp_w - 1 >= 0 and maze[temp_h][temp_w - 1] == '.' and visited[temp_h][temp_w - 1] < 0:
                    visited[temp_h][temp_w - 1] = visited[temp_h][temp_w] + 1
                    q.put((temp_h, temp_w - 1))

print(ans)

Solution (Python):
import math,string,itertools,fractions,heapq,collections,re,array,bisect,sys,copy,functools
import time,random

sys.setrecursionlimit(10**7)
inf = 10**20
eps = 1.0 / 10**10
mod = 10**9+7
mod2 = 998244353
dd = [(-1,0),(0,1),(1,0),(0,-1)]
ddn = [(-1,0),(-1,1),(0,1),(1,1),(1,0),(1,-1),(0,-1),(-1,-1)]

def LI(): return list(map(int, sys.stdin.readline().split()))
def LLI(): return [list(map(int, l.split())) for l in sys.stdin.readlines()]
def LI_(): return [int(x)-1 for x in sys.stdin.readline().split()]
def LF(): return [float(x) for x in sys.stdin.readline().split()]
def LS(): return sys.stdin.readline().split()
def I(): return int(sys.stdin.readline())
def F(): return float(sys.stdin.readline())
def S(): return input()
def pf(s): return print(s, flush=True)
def pe(s): return print(str(s), file=sys.stderr)
def JA(a, sep): return sep.join(map(str, a))
def JAA(a, s, t): return s.join(t.join(map(str, b)) for b in a)


def main():
    h,w = LI()
    a = [[c=='

    def search(s):
        d = collections.defaultdict(lambda: inf)
        d[s] = 0
        q = []
        heapq.heappush(q, (0, s))
        v = collections.defaultdict(bool)
        while len(q):
            k, u = heapq.heappop(q)
            if v[u]:
                continue
            v[u] = True

            for di,dj in dd:
                ni = u[0] + di
                nj = u[1] + dj
                if ni < 0 or ni >= h or nj < 0 or nj >= w or a[ni][nj]:
                    continue
                uv = (ni,nj)
                if v[uv]:
                    continue
                vd = k + 1
                if d[uv] > vd:
                    d[uv] = vd
                    heapq.heappush(q, (vd, uv))

        return d

    r = 0
    for i in range(h):
        for j in range(w):
            if a[i][j]:
                continue
            d = search((i,j))
            t = max(d.values())
            if r < t:
                r = t

    return r


print(main())

Solution (Python):
H,W=map(int,input().split())
grid=[None]*H
for i in range(H):
  grid[i]=input()

ans=0
from collections import deque
for i in range(H):
  for j in range(W):
    q=deque()
    q.append([i,j,0])
    seen=[[False for j in range(W)] for i in range(H)]
    while q:
      node=q.popleft()
      y=node[0]
      x=node[1]
      dist=node[2]
      if grid[y][x]=="
        continue
      if seen[y][x]:
        continue
      seen[y][x]=True
      if dist>ans:
        ans=dist
      cases=((0,1),(0,-1),(1,0),(-1,0))
      for c in cases:
        if 0<=y+c[0]<H and 0<=x+c[1]<W:
          q.append([y+c[0],x+c[1],dist+1])
      
print(ans)

Solution (Python):
import numpy as np

H, W = list(map(int, input().split()))

tbl = np.zeros([H, W], dtype=np.uint8)
for col in tbl:
	x = input().replace('.', '1').replace('
	col[:] = list(x)

def func(y,x):
    dp = np.ones([H, W]) * np.inf
    data = tbl.copy()
    data[y,x] = 0
    dp[y,x] = 0

    que = [[y,x]]

    def move(i, j, m, n):
        if m<0 or n<0 or m>=H or n>=W:
            return

        if data[m, n] == 1:
            data[m, n] = 0
            dp[m, n] = min(dp[i, j] + 1, dp[m, n])
            que.append([m, n])

    while len(que) > 0:
        i, j = que.pop(0)
        move(i,j,i-1,j)
        move(i,j,i+1,j)
        move(i,j,i,j-1)
        move(i,j,i,j+1)
       
    return dp[dp != np.inf].max() 

ans = 0
for i in range(H):
    for j in range(W):
        if tbl[i,j] == 0:
            continue
        
        num = func(i, j)    
        if num != np.inf:
            ans = max(ans, num)
            if ans == H + W - 2:
                break

if ans == np.inf:
	ans = 0
print(int(ans))

Solution (Python):
import heapq
INFTY = 10**3
H,W = map(int,input().split())
S = [input().strip() for _ in range(H)]
dist = {(i,j):{(k,l):INFTY for k in range(H) for l in range(W)} for j in range(W) for i in range(H)}
for i in range(H):
    for j in range(W):
        if S[i][j]==".":
            hist = {(k,l):0 for k in range(H) for l in range(W)}
            heap = [(0,i,j)]
            dist[(i,j)][(i,j)]= 0
            hist[(i,j)] = 1
            while heap:
                d,k,l = heapq.heappop(heap)
                if d>dist[(i,j)][(k,l)]:continue
                hist[(k,l)] = 1
                if l+1<W and S[k][l+1]=="." and hist[(k,l+1)]==0:
                    if dist[(i,j)][(k,l+1)]>d+1:
                        dist[(i,j)][(k,l+1)] = d+1
                        heapq.heappush(heap,(d+1,k,l+1))
                if l-1>-1 and S[k][l-1]=="." and hist[(k,l-1)]==0:
                    if dist[(i,j)][(k,l-1)]>d+1:
                        dist[(i,j)][(k,l-1)]=d+1
                        heapq.heappush(heap,(d+1,k,l-1))
                if k+1<H and S[k+1][l]=="." and hist[(k+1,l)]==0:
                    if dist[(i,j)][(k+1,l)]>d+1:
                        dist[(i,j)][(k+1,l)]=d+1
                        heapq.heappush(heap,(d+1,k+1,l))
                if k-1>-1 and S[k-1][l]=="." and hist[(k-1,l)]==0:
                    if dist[(i,j)][(k-1,l)]>d+1:
                        dist[(i,j)][(k-1,l)]=d+1
                        heapq.heappush(heap,(d+1,k-1,l))
dmax = 0
for i in range(H):
    for j in range(W):
        for k in range(H):
            for l in range(W):
                if dist[(i,j)][(k,l)]<INFTY:
                    dmax = max(dmax,dist[(i,j)][(k,l)])
print(dmax)

Solution (Python):
import sys
from collections import deque
input = sys.stdin.readline
h, w = map(int, input().split())
g = []
for i in range(h):
    g.append(input())

move = ((0, 1), (1, 0), (-1, 0), (0, -1))
ans = 0

for start in  [[i, j] for i in range(h) for j in range(w)]:
    if g[start[0]][start[1]] == "
        continue
    dp = [[0 for i in range(w)] for i in range(h)]
    pre = [-1, -1]
    cur = start
    cnt = 0
    queue = deque([[cur, pre, cnt]])
    while queue:
        cur, pre, cnt = queue.popleft()
        c_x, c_y = cur
        if g[c_x][c_y] == '
          continue
        if not dp[c_x][c_y] or (dp[c_x][c_y] and dp[c_x][c_y] > cnt):
            dp[c_x][c_y] = cnt

            for x, y in move:
                next = [cur[0] + x, cur[1] + y]
                if next == start:
                    continue
                if next != pre and next[0] >= 0 and next[0] < h and next[1] >= 0 and next[1] < w:
                    queue.append([next, cur, cnt + 1])
    ans= max(max([dp[i][j] for i in range(h) for j in range(w)]), ans)


print(ans)

Solution (Python):
from collections import deque
from copy import deepcopy

h, w = map(int, input().split())
INF = float("inf")
s = [list(map(lambda x: -1 if x == "

ans = 0

def bfs(init_y, init_x, s):
    vect = ((-1, 0), (0, -1), (1, 0), (0, 1))
    if s[init_y][init_x] == -1: return 0
    s[init_y][init_x] = 0
    q = deque([(init_y, init_x)])
    while q:
        y, x = q.popleft()
        for dy, dx in vect:
            ny, nx = y + dy, x + dx
            if ny < 0 or ny >= h or nx < 0 or nx >= w or s[ny][nx] != INF: continue
            s[ny][nx] = s[y][x] + 1
            q.append((ny, nx))
    return max(map(max, s))

for i in range(h):
    for j in range(w):
        ans = max(ans, bfs(i, j, deepcopy(s)))

print(ans)

Solution (Python):
class Node:
    def __init__(self, text, pos):
        self.text = text
        self.pos = pos
        self.next_nodes = []

    def add_next(self, node):
        self.next_nodes.append(node)


def all_pats():
    pat = []
    for i in range(H):
        for j in range(W):
            pat.append((i, j))
    return pat


def dfs(start):
    queue = []
    queue.append(start)
    count = dict()
    count[start.pos] = 0

    while True:
        if not queue:
            break
        node = queue[0]
        queue = queue[1:]

        for next_node in node.next_nodes:
            if next_node.pos in count:
                continue
            count[next_node.pos] = count[node.pos] + 1
            queue.append(next_node)
    return max(count.values())


H, W = [int(x) for x in input().split(" ")]
nodes = dict()
for i in range(H):
    for j, text in enumerate(input()):
        nodes[(i, j)] = Node(text, (i, j))


for i in range(H):
    for j in range(W):
        node = nodes[(i, j)]
        if node.text == "
            continue
        for pos in [(i-1, j), (i, j-1), (i+1, j), (i, j+1)]:
            if 0 <= pos[0] <= H-1 and 0 <= pos[1] <= W-1 and nodes[pos].text == ".":
                node.add_next(nodes[pos])


all_pats = all_pats()

counts = []
for start in all_pats:
    counts.append(dfs(nodes[start]))

print(max(counts))

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

ans=0
dx = [1,0,-1,0]
dy = [0,1,0,-1] 
import queue
for si in range(h):
	for sj in range(w):
		if s[si][sj] == "
			continue
		dist = [[-1 for a in range(w)]for b in range(h)]
		q = queue.Queue()
		q.put([si,sj])
		dist[si][sj]=0
		while not q.empty():
			nowi,nowj = q.get()
			for ne in range(4):
				nexti,nextj = nowi+dx[ne],nowj+dy[ne]
				if nexti<0 or nexti>=h or nextj<0 or nextj>=w:
					continue
				if dist[nexti][nextj] != -1 or s[nexti][nextj]=="
					continue
				dist[nexti][nextj] = dist[nowi][nowj]+1
				q.put([nexti,nextj])
				ans = max(ans,dist[nexti][nextj])
print(ans)

Solution (Python):
from itertools import product


def solve(string):
    h, w, *s = string.split()
    h, w = int(h), int(w)
    s = ["
    ans = 0
    d = [(1, 0), (-1, 0), (0, 1), (0, -1)]

    def n(q, cx, cy):
        for x, y in d:
            nx = cx + x
            ny = cy + y
            if s[nx][ny] == ".":
                q.append((nx, ny, cx, cy))

    for _h, _w in product(range(1, h + 1), range(1, w + 1)):
        if s[_h][_w] == "
            continue
        q = list()
        n(q, _h, _w)
        if len(q) > 2:
            continue
        c = [[h * w] * (w + 2) for _ in range(h + 2)]
        c[_h][_w] = 0
        while q:
            cx, cy, px, py = q.pop()
            if c[px][py] + 1 >= c[cx][cy]:
                continue
            c[cx][cy] = c[px][py] + 1
            n(q, cx, cy)
        for i, j in product(range(1, h + 1), range(1, w + 1)):
            ans = max(ans, c[i][j] * (s[i][j] == "."))
    return str(ans)


if __name__ == '__main__':
    import sys
    print(solve(sys.stdin.read().strip()))

Solution (Python):
from itertools import product


def solve(string):
    h, w, *s = string.split()
    h, w = int(h), int(w)
    s = ["
    ans = 0
    d = [(1, 0), (-1, 0), (0, 1), (0, -1)]
    for _h, _w in product(range(1, h + 1), range(1, w + 1)):
        if s[_h][_w] == "
            continue
        q = list()
        for x, y in d:
            if s[_h + x][_w + y] == ".":
                q.append((_h + x, _w + y, _h, _w))
        if len(q) > 2:
            continue
        c = [[h * w] * (w + 2) for _ in range(h + 2)]
        c[_h][_w] = 0
        while q:
            cx, cy, px, py = q.pop()
            if c[px][py] + 1 >= c[cx][cy]:
                continue
            c[cx][cy] = c[px][py] + 1
            for x, y in d:
                nx = cx + x
                ny = cy + y
                if s[nx][ny] == ".":
                    q.append((nx, ny, cx, cy))
        for i, j in product(range(1, h + 1), range(1, w + 1)):
            ans = max(ans, c[i][j] * (s[i][j] == "."))
    return str(ans)


if __name__ == '__main__':
    import sys
    print(solve(sys.stdin.read().strip()))

Solution (Python):
from itertools import product


def solve(string):
    h, w, *s = string.split()
    h, w = map(int, [h, w])
    s = ["
    ans = 0
    d = [(1, 0), (-1, 0), (0, 1), (0, -1)]
    for _h, _w in product(range(1, h + 1), range(1, w + 1)):
        if s[_h][_w] == "
            continue
        q = list()
        for x, y in d:
            if s[_h + x][_w + y] == ".":
                q.append((_h + x, _w + y, _h, _w))
        if len(q) > 2:
            continue
        c = [[h * w] * (w + 2) for _ in range(h + 2)]
        c[_h][_w] = 0
        while q:
            cx, cy, px, py = q.pop()
            if c[px][py] + 1 >= c[cx][cy]:
                continue
            c[cx][cy] = c[px][py] + 1
            for x, y in d:
                if s[cx + x][cy + y] == ".":
                    q.append((cx + x, cy + y, cx, cy))
        for i, j in product(range(1, h + 1), range(1, w + 1)):
            ans = max(ans, c[i][j] * (s[i][j] == "."))
    return str(ans)


if __name__ == '__main__':
    import sys
    print(solve(sys.stdin.read().strip()))

Solution (Python):
from itertools import product


def solve(string):
    h, w, *s = string.split()
    h, w = map(int, [h, w])
    s = ["
    ans = 0
    d = [(1, 0), (-1, 0), (0, 1), (0, -1)]
    for _h, _w in product(range(1, h + 1), range(1, w + 1)):
        if s[_h][_w] == "
            continue
        q = list()
        for x, y in d:
            if s[_h + x][_w + y] == ".":
                q.append((_h + x, _w + y, _h, _w))
        if len(q) > 2:
            continue
        c = [[h * w] * (w + 2) for _ in range(h + 2)]
        c[_h][_w] = 0
        while q:
            cx, cy, px, py = q.pop()
            if c[px][py] + 1 >= c[cx][cy]:
                continue
            c[cx][cy] = c[px][py] + 1
            for x, y in d:
                if s[cx + x][cy + y] == ".":
                    q.append((cx + x, cy + y, cx, cy))
        ans = max(
            ans,
            *(c[i][j] * (s[i][j] == ".") for i, j in product(range(1, h + 1), range(1, w + 1))))
    return str(ans)


if __name__ == '__main__':
    import sys
    print(solve(sys.stdin.read().strip()))

Solution (Python):
from itertools import product


def solve(string):
    h, w, *s = string.split()
    h, w = map(int, [h, w])
    s = ["
    s = ["
    ans = 0
    d = [(1, 0), (-1, 0), (0, 1), (0, -1)]
    for _h, _w in product(range(1, h + 1), range(1, w + 1)):
        if s[_h][_w] == "
            continue
        q = list()
        for x, y in d:
            if s[_h + x][_w + y] == ".":
                q.append((_h + x, _w + y, _h, _w))
        if len(q) > 2:
            continue
        c = [[h * w] * (w + 2) for _ in range(h + 2)]
        c[_h][_w] = 0
        while q:
            cx, cy, px, py = q.pop()
            if c[px][py] + 1 >= c[cx][cy]:
                continue
            c[cx][cy] = c[px][py] + 1
            for x, y in d:
                nx = cx + x
                ny = cy + y
                if s[nx][ny] == ".":
                    q.append((nx, ny, cx, cy))
        for i, j in product(range(1, h + 1), range(1, w + 1)):
            ans = max(ans, c[i][j] * (s[i][j] == "."))
    return str(ans)


if __name__ == '__main__':
    import sys
    print(solve(sys.stdin.read().strip()))

Solution (Python):
from itertools import product


def solve(string):
    h, w, *s = string.split()
    h, w = map(int, [h, w])
    s = ["
    s = ["
    ans = 0
    d = [(1, 0), (-1, 0), (0, 1), (0, -1)]
    for _h, _w in product(range(1, h + 1), range(1, w + 1)):
        if s[_h][_w] == "
            continue
        c = [[h * w] * (w + 2) for _ in range(h + 2)]
        c[_h][_w] = 0
        q = list()
        for x, y in d:
            if s[_h + x][_w + y] == ".":
                q.append((_h + x, _w + y, _h, _w))
        if len(q) > 2:
            continue
        while q:
            cx, cy, px, py = q.pop()
            if c[px][py] + 1 >= c[cx][cy]:
                continue
            c[cx][cy] = c[px][py] + 1
            for x, y in d:
                nx = cx + x
                ny = cy + y
                if s[nx][ny] == ".":
                    q.append((nx, ny, cx, cy))
        for i, j in product(range(1, h + 1), range(1, w + 1)):
            ans = max(ans, c[i][j] * (s[i][j] == "."))
    return str(ans)


if __name__ == '__main__':
    import sys
    print(solve(sys.stdin.read().strip()))

Solution (Python):
h, w = map(int, input().split())
s = [list(input()) for i in range(h)]

def route(l):
  routeout = []
  if l[0] > 0:
    if sc[l[1]][l[0]-1] == '.':
      routeout.append([l[0]-1, l[1]])
  if l[0] < w-1:
    if sc[l[1]][l[0]+1] == '.':
      routeout.append([l[0]+1, l[1]])
  if l[1] > 0:
    if sc[l[1]-1][l[0]] == '.':
      routeout.append([l[0], l[1]-1])
  if l[1] < h-1:
    if sc[l[1]+1][l[0]] == '.':
      routeout.append([l[0], l[1]+1])
  return routeout

def f(linl, out):
  nextxy = []
  for l in linl:
    nextxy += route(l)
    for ll in route(l):
      sc[ll[1]][ll[0]] = '
  if len(nextxy)>0:
    return f(nextxy, out+1)
  else:
    return out
  
r = set()
for i in range(h):
  for j in range(w):
    if s[i][j] == '.':
      sc = [[l for l in ll] for ll in s]
      sc[i][j] = '
      r.add(f([[j, i]], 0))
print(max(r))

Solution (Python):
n, m = map(int, input().split())
ar = []
for i in range(n):
    ar.append(list(input()))

dx = [1, -1, 0, 0]
dy = [0, 0, -1, 1]
res  = 0


for i in range(n):
    for j in range(m):
        if ar[i][j] == '.':
            vis = [[-1] * m for k in range(n)]
            queue = [i, j]
            vis[i][j] = 0
            while len(queue):
                x = queue.pop(0)
                y = queue.pop(0)
                for k in range(4):
                    x1 = x + dx[k]
                    y1 = y + dy[k]
                    if 0 <= x1 < n and 0 <= y1 < m and ar[x1][y1] == '.' and vis[x1][y1] == -1:
                        vis[x1][y1] = vis[x][y] + 1
                        res = max(res, vis[x1][y1])
                        queue.append(x1)
                        queue.append(y1)

print(res)

Solution (Python):
h,w=map(int, input().split())
g={}
for i in range(h):
    l=input()
    length=len(l)
    for j,x in enumerate(l):
        if x == '
            continue
        pos=length*i+j
        g[pos]=[]
        if pos-1 in g.keys() and pos % length != 0:
            g[pos-1].append(pos)
            g[pos].append(pos-1)
        if pos-length in g.keys():
            g[pos-length].append(pos)
            g[pos].append(pos-length)

counts = []
for i in g.keys():
    l = [i]
    done = []
    count = 0
    while len(l):
        for _ in range(len(l)):
            x = l.pop(0)
            done.append(x)
            for y in g[x]:
                if y in done:
                    continue
                if y in l:
                    continue
                l.append(y)
        count=count+1
    counts.append(count)
print(max(map(lambda x: x-1, counts)))

Solution (Python):
import numpy as np
from copy import deepcopy
temp=list(map(int, input().split()))
R=temp[0]
C=temp[1]

color=np.zeros((R,C)).astype(int)

for i in range(R):
  temp=input()
  a=np.zeros(C).astype(int)
  for j in range(C):
      if temp[j]=='
        a[j]=1
      else:
        a[j]=0
  color[i]=a
  
def Adj(u):
  adj=[]
  for v in [(u[0]-1,u[1]),(u[0]+1,u[1]),(u[0],u[1]-1),(u[0],u[1]+1)]:
      if v[0]>=0 and v[0]<R and v[1]>=0 and v[1]<C:
        adj.append(v)
  return adj  

def BFS(s,c,d):
  Q=[s]
  while Q !=[]:
    u=Q[0]
    del Q[0]
    for v in Adj(u):  
      if c[v[0],v[1]]==0:
        c[v[0],v[1]]=1
        d[v[0],v[1]]=d[u[0],u[1]]+1
        Q.append(v)
        
def main():
  ma=0
  for sx in range(R):
    for sy in range(C):
      if color[sx,sy]==0:
        d=np.zeros((R,C)).astype(int)
        c=deepcopy(color)
        c[sx,sy]=1
        BFS((sx,sy),c,d)
        ma=max(np.max(d),ma)
  print(ma)

main()