hdu2822

简单题；

优先队列:如果为"."step+1，为”X“不加；搜素即可；

 

 

#include<stdio.h>
#include<queue>
#define N 1002
using namespace std;
struct node
{
    int x,y,step;
    friend bool operator<(node n1,node n2)
    {
        return n2.step<n1.step;
    }
};
char map[N][N];
int a,b,sx,sy;
int tox[4][2]={0,1,0,-1,1,0,-1,0};
int bfs(int x,int y)
{
    priority_queue<node>q;
    node cur,next;
    int k;
    cur.x=x;
    cur.y=y;
    cur.step=0;
    q.push(cur);
    map[x][y]='*';
    while(!q.empty())
    {
        cur=q.top();
        q.pop();
        for(k=0;k<4;k++)
        {
            x=next.x=cur.x+tox[k][0];
            y=next.y=cur.y+tox[k][1];
            if(x>=0&&x<a&&y>=0&&y<b&&map[x][y]!='*')
            {
                if(x==sx-1&&y==sy-1)
                    return cur.step;
                if(map[x][y]=='.')
                    next.step=cur.step+1;
                else
                    next.step=cur.step;
                q.push(next);
                map[x][y]='*';
            }
        }
    }
    return -1;
}
int main ()
{
    int i,x,y,res;
    while(scanf("%d%d",&a,&b),a||b)
    {
        for(i=0;i<a;i++)
            scanf("%s",map[i]);
        scanf("%d%d",&x,&y);
        scanf("%d%d",&sx,&sy);
        if(x==sx&&y==sy)
            res=0;
        else
            res=bfs(x-1,y-1);
        printf("%d\n",res);
    }
    return 0;
}