So easy

用BFS算法

#include<iostream>
#include<queue>
#include<cstring>
using namespace std;
int N,M,sx,sy,fx,fy;
char a[2005][2005];
bool vis[2005][2005];
int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};
struct node{
    int x,y,step;
};
int BFS(){
    queue<node> q;
    q.push({sx,sy,0});
    vis[sx][sy]=true;
    while(q.size()){
        node now=q.front();
        q.pop();
        if(now.x==fx&&now.y==fy){
            return now.step;
        }
        for(int i=0;i<4;i++){
            int nx=now.x+dx[i];
            int ny=now.y+dy[i];
            if(nx<1||nx>2000||ny<1||ny>2000){
                continue;
            }
            if(!vis[nx][ny]&&a[nx][ny]!='#'){
                vis[nx][ny]=true;
                q.push({nx,ny,now.step+1});
            }
        }
    }
    return -1;
}
int main(){
    cin>>M>>N;
    for(int i=1;i<=M;i++){
        for(int j=1;j<=N;j++){
            cin>>a[i][j];
            if(a[i][j]=='@'){
                sx=i;
                sy=j;
            }
            if(a[i][j]=='*'){
                fx=i;
                fy=j;
            }
        }
    }
    memset(vis,false,sizeof(vis));
    int result=BFS();
    cout<<result;
}