HDU 1242 Rescue(BFS)

题目链接

Problem Description

Angel was caught by the MOLIGPY! He was put in prison by Moligpy. The prison is described as a N * M (N, M <= 200) matrix. There are WALLs, ROADs, and GUARDs in the prison.

Angel‘s friends want to save Angel. Their task is: approach Angel. We assume that "approach Angel" is to get to the position where Angel stays. When there‘s a guard in the grid, we must kill him (or her?) to move into the grid. We assume that we moving up, down, right, left takes us 1 unit time, and killing a guard takes 1 unit time, too. And we are strong enough to kill all the guards.

You have to calculate the minimal time to approach Angel. (We can move only UP, DOWN, LEFT and RIGHT, to the neighbor grid within bound, of course.)

Input

First line contains two integers stand for N and M.

Then N lines follows, every line has M characters. "." stands for road, "a" stands for Angel, and "r" stands for each of Angel‘s friend.

Process to the end of the file.

Output

For each test case, your program should output a single integer, standing for the minimal time needed. If such a number does no exist, you should output a line containing "Poor ANGEL has to stay in the prison all his life."

Sample Input

7 8

#.#####.

#.a#..r.

#..#x...

..#..#.#

#...##..

.#......

........

Sample Output

13

题解：a是目标位置，r是起始位置，通过x需要多1s时间，如果走不到输出"Poor ANGEL has to stay in the prison all his life."。

#include <cstdio>
#include <iostream>
#include <string>
#include <sstream>
#include <cstring>
#include <stack>
#include <queue>
#include <algorithm>
#include <cmath>
#include <map>
#define PI acos(-1.0)
#define ms(a) memset(a,0,sizeof(a))
#define msp memset(mp,0,sizeof(mp))
#define msv memset(vis,0,sizeof(vis))
using namespace std;
//#define LOCAL
int n,m;
char mp[210][210];
int dir[4][2]= {{0,1},{0,-1},{1,0},{-1,0}};
int ex,ey;
int vis[210][210];
struct Node
{
    int x,y;
    int time;
} cp;
int bfs()
{
    queue<Node> q;
    while(!q.empty())q.pop();
    q.push(cp);
    while(!q.empty())
    {
        cp=q.front(),q.pop();
        if(cp.x==ex&&cp.y==ey)return cp.time;
        vis[cp.x][cp.y]=1;
        for(int i=0; i<4; i++)
        {
            Node np;
            np.x=cp.x+dir[i][0];
            np.y=cp.y+dir[i][1];
            np.time=cp.time+1;
            if(mp[np.x][np.y]==‘#‘)continue;
            if(vis[np.x][np.y])continue;
            if(np.x<0||np.y<0||np.x>=n||np.y>=m)continue;
            if(mp[np.x][np.y]==‘x‘)np.time++;
            q.push(np);
        }
    }
    return -1;
}
int main()
{
#ifdef LOCAL
    freopen("in.txt", "r", stdin);
#endif // LOCAL
    ios::sync_with_stdio(false);
    while(cin>>n>>m)
    {
        msp,msv;
        for(int i=0; i<n; i++)cin>>mp[i];
        for(int i=0; i<n; i++)
            for(int j=0; j<m; j++)
            {
                if(mp[i][j]==‘a‘)ex=i,ey=j;
                else if(mp[i][j]==‘r‘)cp.x=i,cp.y=j;
            }
        cp.time=0;
        vis[cp.x][cp.y]=1;
        int ans=bfs();
        if(ans==-1)printf("Poor ANGEL has to stay in the prison all his life.\n");
        else printf("%d\n",ans);
    }
    return 0;
}