hdu1242（BFS+优先队列）

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#include<stdio.h>
#include<string.h>
#include<algorithm>
#include<queue>
using namespace std;
int n,m;
const int maxn = 500;
char s[maxn][maxn];
int d[maxn][maxn];
int dx[4]={0,1,0,-1};
int dy[4]={1,0,-1,0};
typedef pair<int,int> pr;
struct node{
    int x,y;
    int time;
    node(int x,int y,int time):x(x),y(y),time(time){}
    bool operator < (const node &a) const
    {
        return time>a.time;
    }
};
const int oo = 0x3f3f3f3f;
int bfs(int sx,int sy)
{
    for(int i=0; i<maxn; i++)
        for(int j=0; j<maxn; j++)
            d[i][j] = oo;
    priority_queue<node>q;
    d[sx][sy] = -1;
    q.push(node(sx,sy,0));
    while(!q.empty())
    {
        node tmp = q.top();
        q.pop();
        if(s[tmp.x][tmp.y]=='r')
            return tmp.time;
        for(int i=0; i<4; i++)
        {
            int tx = tmp.x+dx[i];
            int ty = tmp.y+dy[i];
            if(tx>=0&&tx<n&&ty>=0&&ty<m&&s[tx][ty]!='#'&&d[tx][ty]==oo)
            {
                if(s[tx][ty]=='x')
                    q.push(node(tx,ty,tmp.time+2));
                else
                    q.push(node(tx,ty,tmp.time+1));
                d[tx][ty] = -1;
            }
        }
    }
    return -1;
}
int main()
{
    while(~scanf("%d%d",&n,&m))
    {
        for(int i=0; i<n; i++)
        {
            scanf("%s",s[i]);
        }
        int ans = -1;
        for(int i=0; i<n; i++)
        {
            for(int j=0; j<m; j++)
                if(s[i][j]=='a')
                {
                    ans = bfs(i,j);
                    break;
                }
        }
        if(ans == -1)
            printf("Poor ANGEL has to stay in the prison all his life.n");
        else
            printf("%dn",ans);
    }
    return 0;
}