hdu 1175 连连看

AC代码：

#include <iostream>
#include <cstdio>
#include <cstring>
#include <queue>
using namespace std;

const int dx[] = {-1,0,1,0},dy[] = {0,1,0,-1};
//醉了，醉了，居然败给扩展顺序上了
//原来的const int dx[] = {-1,0,1,0},dy[] = {0,-1,0,1};
/*
3 4
1 1 0 5
0 0 0 0
5 0 1 0
2
3 1 1 4
1 4 3 1 
*/
struct node{
    int x,y;
    int dir;
    int cnt;
};
int n,m;
int maze[1005][1005];
int vis[1005][1005];

int bfs(int x1,int y1,int x2,int y2){
    memset(vis,0,sizeof(vis));
    queue<node> q;
    node cur;
    q.push(node{x1,y1,-1,0});
    vis[x1][y1] = 1;
    while(!q.empty()){
        cur = q.front();
        q.pop();
        if(cur.cnt > 3)
            continue;
        for(int i = 0; i < 4; i++){
            int xx = cur.x+dx[i],yy = cur.y+dy[i],flag = 0;
            if(xx <= 0 || xx > n || yy <= 0 || yy > m)
                continue;
            if(cur.dir != i){
                flag = 1;
            }
            if(xx == x2 && yy == y2 && cur.cnt+flag <= 3)
                return 1;
            if(maze[xx][yy] || vis[xx][yy])
                continue;
            if(cur.dir != i){
                flag = 1;
            }
            q.push(node{xx,yy,i,cur.cnt+flag});
            vis[xx][yy] = 1;
        }
    }
    return -1;
}

int main(){
    while(scanf("%d%d",&n,&m),n+m){
        for(int i = 1; i <= n; i++){
            for(int j = 1; j <= m; j++){
                scanf("%d",&maze[i][j]);
            }
        }
        int q;
        scanf("%d",&q);
        while(q--){
            int x1,y1,x2,y2;
            scanf("%d%d%d%d",&x1,&y1,&x2,&y2);
            if(maze[x1][y1] != maze[x2][y2] || !(maze[x1][y1]+maze[x2][y2])){
                printf("NO\n");
                continue;
            }
            int ans = bfs(x1,y1,x2,y2);
            if(ans < 0)
                printf("NO\n");
            else
                printf("YES\n");
        }
    }
    return 0;
}