深搜dfs 题解 100% AC

#include<iostream>
using namespace std;
int dx[4]={0,1,0,-1},dy[4]={1,0,-1,0};
int n,a[110][110],sx,sy,fx,fy;
char b[110][110];
bool vis[110][110],flag;
void dfs(int x,int y){
    if(x==fx&&y==fy){
        flag=1;
        return;
    }
    for(int i=0;i<4;i++){
        int nx=x+dx[i],ny=y+dy[i];
        if(nx<1||ny<1||nx>n||ny>n||vis[nx][ny]||a[nx][ny]) continue;
        else{
            vis[nx][ny]=1;
            dfs(nx,ny);
        }
    }
}
int main() {
    cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            cin>>b[i][j];
            if(b[i][j]=='#') a[i][j]=1;
        }
    }
    cin>>sx>>sy>>fx>>fy;
    sx++;sy++;fx++;fy++;
    vis[sx][sy]=1;
    if(a[sx][sy]||a[fx][fy]){
        cout<<"no";
        return 0;
    }
    dfs(sx,sy);
    if(flag)cout<<"yes";
    else cout<<"no";
	return 0;
}