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.



Sample input:
3 3
...
...
...


Sample output:
4

Submission status: Accepted

Solution code:
from collections import deque
from itertools import product

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

points = [(y, x) for y, x in product(range(H), range(W)) if maze[y][x] == '.']

ans = 0
for sy, sx in points:
    costs = {}
    queue = deque()
    queue.append((sy, sx, 0))
    while queue:
        y, x, cost = queue.popleft()
        if (y, x) in costs:
            continue
        else:
            costs[(y, x)] = cost

        for ny, nx in ((y + 1, x), (y - 1, x), (y, x + 1), (y, x - 1)):
            if not 0 <= ny < H:
                continue
            if not 0 <= nx < W:
                continue
            if (ny, nx) in costs:
                continue
            if maze[ny][nx] == '#':
                continue
            queue.append((ny, nx, cost + 1))

    ans = max(ans, max(costs.values()))

print(ans)

Submission status: Accepted

Solution code:
from collections import Counter, defaultdict
import sys

sys.setrecursionlimit(10 ** 5 + 10)
input = sys.stdin.readline
from math import factorial
import heapq, bisect
import math
import itertools
from copy import deepcopy
import queue
from collections import deque


def maxload(data_copy, i, j, high, width):
    data = deepcopy(data_copy)
    count = 0
    now_point = set()
    now_point.add((i, j))
    next_point = set()

    move = [[1, 0], [0, 1], [-1, 0], [0, -1]]

    while len(now_point):
        for now_i, now_j in now_point:
            data[now_i][now_j] = count
            for move_i, move_j in move:
                next_i, next_j = now_i + move_i, now_j + move_j
                if next_i < 0 or next_i >= high or next_j < 0 or next_j >= width:
                    continue
                if data[next_i][next_j] != ".":
                    continue
                next_point.add((next_i, next_j))

        now_point = next_point
        next_point = set()
        count += 1

    return count - 1



def main():
    high, width = map(int, input().split())
    data = [list(input()) for i in range(high)]

    ans = 0

    for i in range(high):
        for j in range(width):
            if data[i][j] == "#":
                continue
            ans = max(ans, maxload(data, i, j, high, width))

    print(ans)


if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
from math import ceil,floor,comb,factorial,gcd,sqrt,log2,cos,sin,tan,acos,asin,atan,degrees,radians,pi,inf
from itertools import accumulate,permutations,combinations,product,combinations_with_replacement
from collections import deque,defaultdict,Counter
from bisect import bisect_left,bisect_right
from operator import itemgetter
from heapq import heapify,heappop,heappush
from queue import Queue,LifoQueue,PriorityQueue
from copy import deepcopy
from time import time
import string
import sys
sys.setrecursionlimit(10 ** 7)
def input() : return sys.stdin.readline().strip()
def INT()   : return int(input())
def MAP()   : return map(int,input().split())
def LIST()  : return list(MAP())

def bfs():
    d = [[inf]*w for i in range(h)]

    dy = [0, 1, 0, -1]
    dx = [1, 0, -1, 0]
 
    que = deque([])
    que.append((sy, sx))
    d[sy][sx] = 0
    ret = 0
 
    while que:
        p = que.popleft()
        for i in range(4):
            ny = p[0] + dy[i]
            nx = p[1] + dx[i]
 
            if 0 <= ny < h and 0 <= nx < w and maze[ny][nx] != '#' and d[ny][nx] == inf:
                que.append((ny,nx))
                d[ny][nx] = d[p[0]][p[1]] + 1
                ret = max(ret, d[ny][nx])
 
    return ret

h, w = MAP()
maze = [input() for i in range(h)]
ans = 0

for sy in range(h):
    for sx in range(w):
        if maze[sy][sx] == '#':
            continue
        else:
            ans = max(ans, bfs())

print(ans)

Submission status: Accepted

Solution code:
import collections

h,w = map(int,input().split())
field = [["#"] + list(str(input())) + ["#"] for i in range(h)]

field.append(["#"]*(w+2))
field.insert(0,["#"]*(w+2))

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

def f():
    global ans
    s = q.popleft()
    y,x = s[0],s[1]
    for i in range(4):
        newy = y+dy[i]
        newx = x+dx[i]
        if field[newy][newx] == "." and memo[newy][newx] == "#": 
            q.append((newy,newx))
            memo[newy][newx] = memo[y][x] + 1
            ans = max(ans,memo[y][x] + 1)

ans = 0
for i in range(1,h+1):
    for j in range(1,w+1):
        if field[i][j] == "#":
            continue
        q = collections.deque()
        q.append((i,j))
        memo = [["#"]*(w+2) for i in range(h+2)]
        memo[i][j] = 0
        while q:
            f()

print(ans)

Submission status: Accepted

Solution code:
from collections import deque
H, W = map(int, input().split())
field = ''
for i in range(H):
    field += input()

def bfs(start):
    dist = [0] * (H * W)
    q = deque([start])
    while q:
        p = q.popleft()
        c = dist[p] + 1
        if p - W != start and p - W >= 0 and field[p - W] == '.' and dist[p - W] == 0:
            dist[p - W] = c
            q.append(p - W)
        if p + W != start and p + W < H * W and field[p + W] == '.' and dist[p + W] == 0:
            dist[p + W] = c
            q.append(p + W)
        if p - 1 != start and p - 1 >= 0 and field[p - 1] == '.' and dist[p - 1] == 0 and p % W != 0:
            dist[p - 1] = c
            q.append(p - 1)
        if p + 1 != start and p + 1 < H * W and field[p + 1] == '.' and dist[p + 1] == 0 and p % W != W - 1:
            dist[p + 1] = c
            q.append(p + 1)
    return dist[p]

ans = 0
for s in range(H * W):
    if field[s] == '.':
        ans = max(ans, bfs(s))
print(ans)

Submission status: Accepted

Solution code:
import numpy as np
H, W = map(int, input().split())
map_lis = [input() for i in range(H)]
ans = 0

def prob(x,y,h,w):
  if 0<=x<h and 0<=y<w:
    return True
  else:
    return False

def count(x,y,lis):
  if not lis[x][y]:
    return True
  else:
    return False

def maze(x,y,lis):
  if lis[x][y] == ".":
    return True
  else:
    return False

for i in range(H):
  for j in range(W):
    k = 0
    count_lis = np.zeros((H,W))
    num_lis = [[] for i in range(1000)]
    if maze(i,j,map_lis):
      count_lis[i][j] = 1
      num_lis[0].append([i,j])
    while True:
      for l in num_lis[k]:
        if prob(l[0]-1,l[1],H,W) and count(l[0]-1,l[1],count_lis) and maze(l[0]-1,l[1],map_lis):
          num_lis[k+1].append([l[0]-1,l[1]])
          count_lis[l[0]-1][l[1]] = 1
        if prob(l[0],l[1]-1,H,W) and count(l[0],l[1]-1,count_lis) and maze(l[0],l[1]-1,map_lis):
          num_lis[k+1].append([l[0],l[1]-1])
          count_lis[l[0]][l[1]-1] = 1
        if prob(l[0]+1,l[1],H,W) and count(l[0]+1,l[1],count_lis) and maze(l[0]+1,l[1],map_lis):
          num_lis[k+1].append([l[0]+1,l[1]])
          count_lis[l[0]+1][l[1]] = 1
        if prob(l[0],l[1]+1,H,W) and count(l[0],l[1]+1,count_lis) and maze(l[0],l[1]+1,map_lis):
          num_lis[k+1].append([l[0],l[1]+1])
          count_lis[l[0]][l[1]+1] = 1
      new_ans = 0
      for m in num_lis[1:]:
        if m != []:
          new_ans += 1
        if m == []:
          break
      ans = max(ans, new_ans)
      k += 1
      if num_lis[k] == []:
        break
                                     
print(ans)

Submission status: Accepted

Solution code:
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):
    if maze[x][y]=='#':
      continue
    dist = [[0]*W for i in range(H)]
    Q = deque([[x,y]])
    while Q:
      h,w = Q.popleft()
      for i,j in [[1,0],[-1,0],[0,1],[0,-1]]:
        h2,w2 = h+i,w+j
        if 0<=h2<H and 0<=w2<W and dist[h2][w2]==0 and maze[h2][w2]!='#':
          dist[h2][w2] = dist[h][w]+1
          Q.append([h2,w2])
    dist[x][y] = 0
    ans = max(ans, np.max(dist))
print(ans)

Submission status: Accepted

Solution code:
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(len(s)):
    for j in range(len(s[0])):
        if s[i][j] == '#':
            continue
        pre = 0
        p = np.full((h, w), -1)
        p[i][j] = 0
        check = deque([((i, j), 0)])#(from,now, dist)
        while check:
            now, d = check.popleft()
            pre = max(pre, d)
            for k, l in [(1,0), (-1,0),(0,1), (0,-1)]:
                b = now[0] + k
                c = now[1] + l
                if b < 0 or c < 0 or b >= h or c >= w:
                    continue 
                elif p[b][c] == -1 and s[b][c] != '#':
                    check.append(((b, c), d + 1))
                    p[b][c] = d + 1
        ans = max(ans, pre)

print(ans)

Submission status: Accepted

Solution code:
from collections import deque

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

dir = [(-1, 0), (1, 0), (0, -1), (0, 1)]

dist = [[-1] * W for _ in range(H)]

def BFS(y, x):
  """(y, x)からはじめて、道のマスをBFSで最短距離を探す"""
  que = deque()
  que.append((y, x))
  dist[y][x] = 0
  max_dist = 0
  while que:
    sy, sx = que.popleft()  # popleft?
    for dy, dx in dir:
      ny = sy + dy
      nx = sx + dx
      if 0 <= ny < H and 0 <= nx < W and S[ny][nx] != "#" and dist[ny][nx] == -1:
        que.append((ny, nx))
        dist[ny][nx] = dist[sy][sx] + 1
        max_dist = max(max_dist, dist[ny][nx])
  
  return max_dist

max_dist = 0
for sy in range(H):
  for sx in range(W):
    if S[sy][sx] != "#":
      dist = [[-1] * W for _ in range(H)]
      max_dist = max(max_dist, BFS(sy, sx))

print(max_dist)

Submission status: Accepted

Solution code:
from collections import deque

H,W=map(int,input().split())
S=[]
for i in range(H):
  S.append(input())
  
def bfs(s):
  seen = [[0 for i in range(W)] for j in range(H)]
  total = [[0 for i in range(W)] for j in range(H)]
  todo = deque([])
  now = s
  if S[now[0]][now[1]]=='#':return 0
  seen[now[0]][now[1]],total[now[0]][now[1]] = 1,0
  todo.append(now)
  while 1:
    if len(todo)==0:break
    now = todo.popleft()
    for d in [(1,0),(-1,0),(0,1),(0,-1)]:
      new = (now[0]+d[0], now[1]+d[1])
      if new[0]<0 or new[0]>=H:continue
      if new[1]<0 or new[1]>=W:continue
      if seen[new[0]][new[1]]==1:continue
      if S[new[0]][new[1]]=='#':continue
      seen[new[0]][new[1]] = 1
      todo.append(new)
      total[new[0]][new[1]] = total[now[0]][now[1]] + 1
  return max(map(max, total))

MAX=0
for i in range(H):
  for j in range(W):
    s = (i,j)
    max_ = bfs(s)
    if MAX < max_:MAX=max_

print(MAX)

Submission status: Accepted

Solution code:
from collections import deque
h, w = map(int, input().split())
chiz = [[] for _ in range(w)]
for _ in range(h):
    tmp_list = input()
    for i in range(w):
        chiz[i].append(tmp_list[i])
def bfs(i,j):
    ds = [[-1]*h for _ in range(w)]
    dq = deque([(i,j)])
    ds[i][j] = 0
    res = -1
    while dq:
        i,j = dq.popleft()
        for move in [(1,0),(-1,0),(0,-1),(0,1)]:
            if i+move[0] >= 0 and i+move[0] < w and j+move[1] >= 0 and j+move[1] < h:
                if chiz[i+move[0]][j+move[1]]=='.' and ds[i+move[0]][j+move[1]] == -1:
                    ds[i + move[0]][j + move[1]] = ds[i][j] + 1
                    res = max(res,ds[i + move[0]][j + move[1]])
                    dq.append((i + move[0],j + move[1]))
    return res
res = -1
for j in range(h):
    for i in range(w):
        if chiz[i][j]=='.':
            res = max(res, bfs(i,j))
print(res)

Submission status: Accepted

Solution code:
from collections import deque
m=[[1,0],[-1,0],[0,1],[0,-1]]
h,w=map(int,input().split())
l=list()
l.append('#'*(w+2))
for i in range(h):
    j=input()
    l.append('#'+j+'#')
l.append('#'*(w+2))
def bfs(a,b):
  s=[[-1 for j in i] for i in l]
  s[a][b]=0
  q=deque([[a,b]])
  while len(q)>0:
    x,y=q.popleft()
    for i,j in m:
      if l[x+i][y+j]=='.' and s[x+i][y+j]==-1:
        q.append([x+i,y+j])
        s[x+i][y+j]=s[x][y]+1
        num = s[x+i][y+j]
  return num
ans = []
for i in range(h+2):
  for j in range(w+2):
    if l[i][j] == '.':
      ans.append(bfs(i,j))
print(max(ans))

Submission status: Accepted

Solution code:
# !/usr/bin/python3

"""
https://atcoder.jp/contests/abc151/tasks/abc151_d
Maze Master.
"""

from collections import deque
from copy import deepcopy

def bfs(chw, i, j):
    dq = deque()

    dq.append([i, j])
    chw[i][j] = '#'

    dist = [[-1 for _ in range(w)] for _ in range(h)]
    dist[i][j] = 0

    # for each in dist: print(each)

    while dq:
        y, x = dq.popleft()
        for dy, dx in [[1, 0], [-1, 0], [0, 1], [0, -1]]:
            ny = y+dy
            nx = x+dx
            if 0 <= nx < w and 0 <= ny < h and chw[ny][nx] == '.':
                dq.append([ny, nx])
                chw[ny][nx] = '#'
                dist[ny][nx] = dist[y][x]+1

    # for each in dist: print(each)
    temp_ans = 0
    for each in dist:
        temp_ans = max(temp_ans, max(each))

    return temp_ans



def solve(h, w, hw):
    ans = 0
    for i in range(h):
        for j in range(w):
            if hw[i][j] == '.':
                chw = deepcopy(hw)
                dist = bfs(chw, i, j)
                ans = max(dist, ans)
    return ans

if __name__ == "__main__":
    h, w = list(map(int, input().split(" ")))
    hw = [list(input()) for _ in range(h)]
    print(solve(h, w, hw))

Submission status: Accepted

Solution code:
import sys
import math
from collections import deque

sys.setrecursionlimit(1000000)
MOD = 10 ** 9 + 7
input = lambda: sys.stdin.readline().strip()
NI = lambda: int(input())
NMI = lambda: map(int, input().split())
NLI = lambda: list(NMI())
SI = lambda: input()


def make_grid(h, w, num): return [[int(num)] * w for _ in range(h)]


def main():
    H, W = NMI()
    grid = [SI() for _ in range(H)]
    DH = [-1, 1, 0, 0]
    DW = [0, 0, -1, 1]

    def bfs(sh, sw):
        queue = deque()
        seen = make_grid(H, W, -1)
        queue.append([sh, sw])
        seen[sh][sw] = 0
        while queue:
            now_h, now_w = queue.popleft()
            for dh, dw in zip(DH, DW):
                next_h = now_h + dh
                next_w = now_w + dw
                if not(0 <= next_h < H and 0 <= next_w < W):
                    continue
                if seen[next_h][next_w] != -1 or grid[next_h][next_w] == "#":
                    continue
                queue.append([next_h, next_w])
                seen[next_h][next_w] = seen[now_h][now_w] + 1

        return max([max(l) for l in seen])

    ans = 0
    for h in range(H):
        for w in range(W):
            if grid[h][w] == ".":
                ans = max(ans, bfs(h, w))
    print(ans)




if __name__ == "__main__":
    main()

Submission status: Accepted

Solution code:
from collections import deque
h, w = map(int, input().split())
G = [list(input()) for _ in range(h)]
go = [[0,1], [1,0], [0,-1], [-1,0]]

ans = 0
# [h,w]を探索する.
for hi in range(h):
    for wi in range(w):
        # もしスタートが壁なら、各座標への距離の算出は行わない.
        if G[hi][wi] =='#':
            continue
        # BFSにより各座標への距離の算出を行う.
        ## 距離/探索したかを-1で初期化
        dist = [[-1]*w for _ in range(h)]
        ## [hi,wi]の地点の距離は0.
        dist[hi][wi] = 0
        ## 探索用のキューを初期化.
        que = deque([[hi,wi]])
        
        ## キューがなくなるまで以下を行う.
        while que:
            ### 探索する座標[nowhi,nowwi]
            nowhi, nowwi = que.pop()
            ### 探索する方向
            for dh, dw in go:
                #### 迷路からはみ出す箇所は探索しない.
                if not ((0<=nowhi+dh<=h-1) and (0<=nowwi+dw<=w-1)):
                    continue
                #### 通れない箇所は探索しない.
                if G[nowhi+dh][nowwi+dw]=='#':
                    continue
                #### 探索済みの箇所は探索しない.
                if dist[nowhi+dh][nowwi+dw]!=-1:
                    continue
                #### 探索する地点の距離は、現在の距離+1
                dist[nowhi+dh][nowwi+dw] = dist[nowhi][nowwi]+1
                #### キューに新たな探索済みの地点を追加.
                que.appendleft([nowhi+dh, nowwi+dw])
        # 答えはスタート地点を[h,w]で探索した際、最も長くなる距離.
        ans = max(ans, max([max(d) for d in dist]))
print(ans)

Submission status: Accepted

Solution code:
from sys import stdin
nii=lambda:map(int,stdin.readline().split())
lnii=lambda:list(map(int,stdin.readline().split()))
from copy import deepcopy
from collections import deque

h,w=nii()
s=[list(input()) for i in range(h)]

def dfs(cs,i,j):
  que=deque()
  que.append([i,j])

  cs[i][j]='#'

  dist=[[-1 for a in range(w)] for b in range(h)]
  dist[i][j]=0

  while que:
    y,x=que.popleft()
    for dy,dx in [[1,0],[-1,0],[0,1],[0,-1]]:
      ny=y+dy
      nx=x+dx
      if 0<=ny<h and 0<=nx<w and cs[ny][nx]=='.':
        que.append([ny,nx])
        cs[ny][nx]='#'
        dist[ny][nx]=dist[y][x]+1

  t_ans=0
  for a in dist:
    t_ans=max(t_ans,max(a))

  return t_ans

ans=0
for i in range(h):
  for j in range(w):
    if s[i][j]=='.':
      cs=deepcopy(s)
      dist=dfs(cs,i,j)
      ans=max(ans,dist)

print(ans)

Submission status: Accepted

Solution code:
from collections import deque
import numpy as np
H,W = map(int,input().split())
Maze=[list(input()) for i in range(H)]
ans=0
for hi in range(0,H):
    for wi in range(0,W):
        if Maze[hi][wi]=="#":
            continue
        maze1=[[0]*W for _ in range(H)]
        stack=deque([[hi,wi]])
        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 maze1[new_h][new_w]==0:
                    maze1[new_h][new_w]=maze1[h][w]+1
                    stack.append([new_h,new_w])
        
        maze1[hi][wi]=0
        ans=max(ans,np.max(maze1))
print(ans)

Submission status: Accepted

Solution code:
from collections import deque
import copy
H,W= map(int, input().split())
c=[list(input()) for i in range(H)]

max_num=0
move=[[0,1],[0,-1],[1,0],[-1,0]]
for h in range(H):
    for w in range(W):
        if c[h][w]=='.':
            #初期位置#(H,W)
            L=copy.deepcopy(c)
            d=deque([[h,w]])
            L[h][w]='S'

            num=0
            while d:
                num+=1
                for i in range(len(d)):
                    q=d.popleft()
                    for m in move:
                        if 0<=q[0]+m[0]<=H-1 and 0<=q[1]+m[1]<=W-1 and L[q[0]+m[0]][q[1]+m[1]]=='.':
                            L[q[0]+m[0]][q[1]+m[1]]=num

                            d.append([q[0]+m[0],q[1]+m[1]])

           # print(num-1)
            if num-1>=max_num:
                max_num=num-1
print(max_num)

Submission status: Accepted

Solution code:
from copy import deepcopy
from collections import deque
h,w=map(int,input().split())
ss=[]
u=[(-1,0),(1,0),(0,1),(0,-1)]
ans=0
for i in range(h):
    ss.append(list(input()))
for i in range(h):
    for j in range(w):
        s=deepcopy(ss)
        if s[i][j]=="#":
            continue
        if s[i][j]==".":
            tmp=0
            x,y=i,j
            s[x][y]=0
            que=deque()
            que.append([x,y])
            while que:
                x,y=que.popleft()
                for xx,yy in u:
                    nx,ny=x+xx,y+yy
                    if 0<=nx<h and 0<=ny<w:
                        if s[nx][ny]==".":
                            s[nx][ny]=s[x][y]+1
                            if tmp<s[nx][ny]:
                                tmp=s[nx][ny]
                            que.append([nx,ny])
        if tmp>ans:
            ans=tmp
print(ans)

Submission status: Accepted

Solution code:
import sys
input = sys.stdin.readline
INF = 1001001001
from collections import deque

def linput(ty=int, cvt=list):
	return cvt(map(ty,input().split()))

def pad(mxy, wall="#"):
	w = len(mxy[0])
	gp = wall*(w+2)
	re = [gp,]
	re_app = re.append
	for vx in mxy:
		re_app(wall+vx+wall)
	re_app(gp)
	return re

vD = [(0,1),(1,0),(0,-1),(-1,0)]
vQ = deque([])
vQ_app, vQ_popl = vQ.append, vQ.popleft

def main():
	H,W = linput()
	mM = [input().rstrip() for _ in [0,]*H]
	mM = pad(mM)
	
	res = 0
	cnt = 0
	
	for sr in range(1,H+1):
		for sc in range(1,W+1):
			if mM[sr][sc]=="#":
				continue
			mV = [[INF,]*(W+2) for _ in [INF,]*(H+2)]
			mV[sr][sc] = 0
			vQ_app((sr,sc))
			while vQ:
				r,c = vQ_popl()
				now_cost = mV[r][c]
				for dr,dc in vD:
					nr,nc = r+dr, c+dc
					if mM[nr][nc]=="#":
						continue
					if now_cost + 1 < mV[nr][nc]:
						vQ_app((nr,nc))
						mV[nr][nc] = now_cost + 1
						res = max(now_cost+1, res)
		
				cnt += 1
				#print(res,cnt,X,Y,H)
				if cnt>999999: break
	
	print(res)

if __name__ == "__main__":
	main()

Submission status: Accepted

Solution code:
#!usr/bin/env python3
from collections import defaultdict, deque, Counter, OrderedDict
from functools import reduce, lru_cache
import collections, heapq, itertools, bisect
import math, fractions
import sys, copy

def LI(): return [int(x) for x in sys.stdin.readline().split()]
def LI1(): return [int(x) - 1 for x in sys.stdin.readline().split()]
def I(): return int(sys.stdin.readline().rstrip())
def LS(): return [list(x) for x in sys.stdin.readline().split()]
def S(): return list(sys.stdin.readline().rstrip())
def IR(n): return [I() for i in range(n)]
def LIR(n): return [LI() for i in range(n)]
def SR(n): return [S() for i in range(n)]
def LSR(n): return [LS() for i in range(n)]

sys.setrecursionlimit(1000000)
dire = [[1, 0], [0, 1], [-1, 0], [0, -1]]
dire8 = [[1, 0], [1, 1], [0, 1], [-1, 1], [-1, 0], [-1, -1], [0, -1], [1, -1]]
MOD = 1000000007

def main():
    H, W = LI()
    maze = SR(H)

    ans = 0
    for h in range(H):
        for w in range(W):
            if maze[h][w] == '#':
                continue

            q = deque()
            q.append((0, h, w))

            visited = [[False] * W for _ in range(H)]
            visited[h][w] = True

            while q:
                dist, y, x = q.popleft()

                for dy, dx in dire:
                    if y + dy >= 0 and y + dy < H and x + dx >= 0 and x + dx < W:
                        if maze[y + dy][x + dx] == '.' and not visited[y + dy][x + dx]:
                            q.append((dist + 1, y + dy, x + dx))
                            visited[y + dy][x + dx] = True

            ans = max(ans, dist)

    print(ans)

if __name__ == '__main__':
    main()

Submission status: Accepted

Solution code:
H, W = map(int, input().split())
S = []
for _ in range(H):
    S.append(input())

import queue, itertools

dxy = ((1,0), (-1,0), (0,1), (0,-1))
ans = 0
for s in itertools.product(range(H), range(W)):
    if S[s[0]][s[1]] == '#': continue
    
    q = queue.Queue()
    dist = [[-1]*W for _ in range(H)]     

    q.put(s)
    dist[s[0]][s[1]] = 0
    while not q.empty():
        y, x = q.get()         
        for dx, dy in dxy:
            nx, ny = x+dx, y+dy
            if nx<0 or ny<0 or nx>=W or ny>=H or S[ny][nx] == '#' or dist[ny][nx] >= 0: 
                continue
            dist[ny][nx] = dist[y][x] + 1
            q.put((ny, nx))
    
    ans = max(ans, max(map(max, dist)))

print(ans)

Submission status: Accepted

Solution code:
h, w = map(int, input().split())
ma = [ list(input()) for _ in range(h) ]
d = [(1, 0), (-1, 0), (0, 1), (0, -1)]
ans = 0

def bfs(sy, sx):
    if ma[sy][sx] == "#":
        return 0
    q = [[sy, sx, 0]]
    flag = [[0] * w for _ in range(h)]
    flag[sy][sx] = 1
    ans = 0
    while True:
        if len(q) == 0:
            break
        y, x, dist = q.pop(0)
        for dy, dx in d:
            if 0 <= y + dy < h and 0 <= x + dx < w and flag[y + dy][x + dx] == 0 and ma[y + dy][x + dx] == ".":
                flag[y + dy][x + dx] = 1
                q.append([y + dy, x + dx, dist + 1])
                ans = max(ans, dist + 1)

    return ans


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

print(ans)

Submission status: Accepted

Solution code:
import math
from collections import deque

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

S = [list(input()) for _ in range(H)]


def f(h, w):
    memo = [[-1] * W for _ in range(H)]
    lst = deque()
    lst.append((h, w, 0))
    res = 0
    while lst:
        h, w, c = lst.popleft()
        if memo[h][w] >= c: continue
        memo[h][w] = c
        res = max(c, res)
        for x, y in [(1, 0), (0, 1), (-1, 0), (0, -1)]:
            nh = x + h
            nw = y + w
            if nh < 0 or nh >= H: continue
            if nw < 0 or nw >= W: continue
            if memo[nh][nw] > -1: continue
            if S[nh][nw] == '#': continue
            lst.append((nh, nw, c + 1))

    return res

def main():
    ans = 0
    for h in range(H):
        for w in range(W):
            if S[h][w] == '#': continue
            ans = max(ans,f(h,w))
    return ans
print(main())

Submission status: Accepted

Solution code:
import sys
from io import StringIO
import unittest
import os
from collections import deque

# 再帰処理上限(dfs作成時に設定するのが面倒なので限度近い値を組み込む)
sys.setrecursionlimit(999999999)


# 実装を行う関数
def resolve(test_def_name=""):
    # 数値取得サンプル
    #   1行1項目 n = int(input())
    #   1行2項目 h, w = map(int, input().split())
    #   1行N項目 x = list(map(int, input().split()))
    #   N行1項目 x = [int(input()) for i in range(n)]
    #   N行N項目 x = [list(map(int, input().split())) for i in range(n)]

    # 文字取得サンプル
    #   1行1項目 x = input()
    #   1行1項目(1文字ずつリストに入れる場合) x = list(input())
    h, w = map(int, input().split())
    maze = [list(input()) for i in range(h)]

    start_list = []
    for i_len, i in enumerate(range(h)):
        for j_len, j in enumerate(range(w)):
            route = 4
            # 自分が壁なら対象外
            if maze[i][j] == "#":
                continue

            # 上下端なら-1
            route -= 1 if i_len == 0 else 0
            route -= 1 if i_len + 1 == h else 0
            # 上下が壁なら-1
            route -= 1 if not i_len == 0 and maze[i - 1][j] == "#" else 0
            route -= 1 if not i_len + 1 == h and maze[i + 1][j] == "#" else 0
            # 左右端なら-1
            route -= 1 if j_len == 0 else 0
            route -= 1 if j_len + 1 == w else 0
            # 左右が壁なら-1
            route -= 1 if not j_len == 0 and maze[i][j - 1] == "#" else 0
            route -= 1 if not j_len + 1 == w and maze[i][j + 1] == "#" else 0
            if route <= 2:
                start_list.append((i, j))

    ans = 0
    que = deque()
    for start in start_list:
        que.appendleft(start)
        ed_list = [[-1 for i in range(w)] for j in range(h)]
        ed_list[start[0]][start[1]] = 0

        # BFS開始
        while len(que) is not 0:
            now = que.pop()

            # 各方向に移動
            for i, j in [(1, 0), (0, 1), (0, -1), (-1, 0)]:
                # 処理対象の座標
                target = [now[0] + i, now[1] + j]

                # 処理対象のチェック
                # 外なら何もしない
                if not 0 <= target[0] < h or not 0 <= target[1] < w:
                    continue

                # 距離が設定されているなら何もしない
                if ed_list[target[0]][target[1]] != -1:
                    continue

                # 壁なら何もしない
                if maze[target[0]][target[1]] == "#":
                    continue

                # 処理対象に対する処理
                # キューに追加(先頭に追加するのでappendleft())
                que.appendleft(target)
                # 距離を設定(現在の距離+1)
                ed_list[target[0]][target[1]] = ed_list[now[0]][now[1]] + 1
                ans = max(ans, ed_list[target[0]][target[1]])

    print(ans)


# テストクラス
class TestClass(unittest.TestCase):
    def assertIO(self, assert_input, output):
        stdout, sat_in = sys.stdout, sys.stdin
        sys.stdout, sys.stdin = StringIO(), StringIO(assert_input)
        resolve(sys._getframe().f_back.f_code.co_name)
        sys.stdout.seek(0)
        out = sys.stdout.read()[:-1]
        sys.stdout, sys.stdin = stdout, sat_in
        self.assertEqual(out, output)

    def test_input_1(self):
        test_input = """3 3
...
...
..."""
        output = """4"""
        self.assertIO(test_input, output)

    def test_input_2(self):
        test_input = """3 5
...#.
.#.#.
.#..."""
        output = """10"""
        self.assertIO(test_input, output)

    # 自作テストパターンのひな形(利用時は「tes_t」のアンダーバーを削除すること
    def test_1original_1(self):
        test_input = """1 2
.."""
        output = """1"""
        self.assertIO(test_input, output)


# 実装orテストの呼び出し
if __name__ == "__main__":
    if os.environ.get("USERNAME") is None:
        # AtCoder提出時の場合
        resolve()

    else:
        # 自PCの場合
        unittest.main()