仙岛求药

#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <queue>
using namespace std;
typedef pair<int,int>PII;

#define x first
#define y second
const int N = 310;
int d[N][N];
char g[N][N];
int n,m;
int bfs(PII start)
{
    queue<PII>q;
    int dx[4]={-1,0,1,0},dy[4]={0,1,0,-1};
    memset(d,-1,sizeof d);
    q.push(start);
    d[start.x][start.y]=0;
    while (q.size())
    {
        PII t = q.front();
        q.pop();
        for (int i=0;i<4;i++)
        {
            int x = t.x+dx[i];
            int y = t.y+dy[i];
            if (x<0||x>=n||y<0||y>=m) continue;
            if (g[x][y]=='#') continue;
            if (d[x][y]!=-1) continue;
            d[x][y]=d[t.x][t.y]+1;
            if (g[x][y]=='*') return d[x][y];
            q.push({x,y});
        }
    }
    return -1;
}
int main()
{
    while (scanf("%d%d",&n,&m),n||m)
    {
        for (int i=0;i<n;i++) scanf("%s",g[i]);
        PII start;
        for (int i=0;i<n;i++)
            for (int j=0;j<m;j++)
                if (g[i][j]=='@') start={i,j};
        int ans=bfs(start);
        printf("%d\n",ans);
    }
    return 0;
}