HDU 2822 (BFS+优先队列)

#include "cstdio"
#include "queue"
#include "cstring"
using namespace std;
#define maxn 1005
bool vis[maxn][maxn];
char map[maxn][maxn];
int n,m,dir[4][2]={-1,0,1,0,0,-1,0,1},sx,sy,ex,ey;
struct status
{
    int x,y,dep;
    status(int x,int y,int dep):x(x),y(y),dep(dep) {}
    bool operator < (const status &a) const {return dep>a.dep;}
};
int bfs()
{
   priority_queue<status> Q;Q.push(status(sx,sy,0));
   vis[sx][sy]=true;
   while(!Q.empty())
   {
       status t=Q.top();Q.pop();
       for(int s=0;s<4;s++)
       {
           int X=t.x+dir[s][0],Y=t.y+dir[s][1];
           if(X<1||X>n||Y<1||Y>m||vis[X][Y]) continue;
           int cost=map[X][Y]==‘.‘?1:0;
           if(X==ex&&Y==ey) return t.dep+cost;
           vis[X][Y]=true;
           Q.push(status(X,Y,t.dep+cost));
       }
   }
   return -1;
}
int main()
{
    //freopen("in.txt","r",stdin);
    while(scanf("%d%d",&n,&m)&&n)
    {
        memset(vis,0,sizeof(vis));
        for (int i=1;i<=n;i++) scanf("%s",map[i]+1);
        scanf("%d%d%d%d",&sx,&sy,&ex,&ey);
        int ans=bfs();
        printf("%d\n",ans);
    }
}