POJ 1383 Labyrinth

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cstring>
 4 #include <cmath>
 5 #include <algorithm>
 6 #include <climits>
 7 #include <vector>
 8 #include <queue>
 9 #include <cstdlib>
10 #include <string>
11 #include <set>
12 #include <stack>
13 #define LL long long
14 #define pii pair<int,int>
15 #define INF 0x3f3f3f3f
16 using namespace std;
17 const int maxn = 1010;
18 char mp[maxn][maxn];
19 int col,row,vis[maxn][maxn],tx,ty;
20 const int dir[4][2] = {-1,0,1,0,0,1,0,-1};
21 queue< pii > q;
22 int bfs(int sx,int sy){
23     while(!q.empty()) q.pop();
24     q.push(make_pair(sx,sy));
25     memset(vis,-1,sizeof(vis));
26     vis[sx][sy] = 0;
27     int mxlen = 0;
28     while(!q.empty()){
29         int x = q.front().first;
30         int y = q.front().second;
31         q.pop();
32         if(vis[x][y] > mxlen) mxlen = vis[tx = x][ty = y];
33         for(int i = 0; i < 4; ++i){
34             int nx = x + dir[i][0];
35             int ny = y + dir[i][1];
36             if(mp[nx][ny] == ‘#‘ || vis[nx][ny] > -1) continue;
37             vis[nx][ny] = vis[x][y] + 1;
38             q.push(make_pair(nx,ny));
39         }
40     }
41     return mxlen;
42 }
43 int main() {
44     int T;
45     scanf("%d",&T);
46     while(T--){
47         scanf("%d %d",&col,&row);
48         for(int i = 0; i < row; ++i)
49             scanf("%s",mp[i]);
50         bool flag = true;
51         for(int i = 1; flag&&i < row; ++i){
52             for(int j = 1; flag&&j < col; ++j){
53                 if(mp[i][j] == ‘.‘){
54                     flag = false;
55                     bfs(i,j);
56                     printf("Maximum rope length is %d.\n",bfs(tx,ty));
57                 }
58             }
59         }
60     }
61     return 0;
62 }