uva 11624 Fire! 【 BFS 】

按白书上说的，先用一次bfs,求出每个点起火的时间

再bfs一次求出是否能够走出迷宫

 #include<cstdio>
 #include<cstring>
 #include<iostream>
 #include<algorithm>
 #include<queue>
 #include<vector>
 using namespace std;
 
 const int maxn = ;
 const int INF = << -;
 int r,c;//r行，c列
 int d[maxn][maxn];
 int vis[maxn][maxn];
 char g[maxn][maxn];
 int sx,sy;
 
 int dir[][] = {,,-,,,,,-};
 
 struct node{
     int x,y;
     int step;
 }p[maxn];
 
 queue<node> Q;
 
 void bfs1(){
     memset(vis,,sizeof(vis));
     while(!Q.empty()){
             node v = Q.front();Q.pop();
             for(int i = ;i < ;i++){
                 int xx = v.x + dir[i][];
                 int yy = v.y + dir[i][];
                 if(xx <  || xx > r || yy <  || yy > c || vis[xx][yy] || g[xx][yy] != '.') continue;
                 vis[xx][yy] = ;
                 d[xx][yy] = min(d[xx][yy],v.step+);
                 Q.push(node{xx,yy,v.step+});
             }
     }
 }
 
 void bfs2(){
     queue<node> q;
     memset(vis,,sizeof(vis));
     q.push(node{sx,sy,});vis[sx][sy] = ;
 
     while(!q.empty()){
         node u = q.front();q.pop();
         if(u.x == r || u.y == c || u.x ==  || u.y == ){
             printf("%d\n",u.step + );
             return;
         }
         for(int i = ;i < ;i++){
             int xx = u.x + dir[i][];
             int yy = u.y + dir[i][];
             if(xx <  || xx > r || yy <  || yy > c || vis[xx][yy] || g[xx][yy] != '.') continue;
             if(u.step +  >= d[xx][yy]) continue;
             vis[xx][yy] = ;
             q.push(node{xx,yy,u.step+});
         }
     }
     puts("IMPOSSIBLE");
 }
 
 int main(){
     int T;
     scanf("%d",&T);
     while(T--){
         while(!Q.empty()) Q.pop();
         scanf("%d %d",&r,&c);
         for(int i = ;i <= r;i++){
             for(int j = ;j <= c;j++) d[i][j] = INF;
         }
         for(int i = ;i <= r;i++){
             for(int j = ;j <= c;j++) {
                 cin>>g[i][j];
                 if(g[i][j] == 'F') Q.push(node{i,j,});
                 if(g[i][j] == 'J') sx = i,sy = j;
             }
         }
         bfs1();
         bfs2();
     }
     return ;
 } 

加油～～～gooooooo~~