BFS做法

#include<bits/stdc++.h>
using namespace std;
int a[35][35];
bool vis[35][35];
int dx[4]={-1,1,0,0};
int dy[4]={0,0,-1,1};
int n;
struct node{
    int x,y;
};

void BFS(int x,int y){
    queue<node>q;
    q.push({x,y});
    while(!q.empty()){
        node now=q.front();
        q.pop();
        for(int i=0;i<4;i++){
            int nx=now.x+dx[i];
            int ny=now.y+dy[i];
            if(nx>=0&&ny>=0&&nx<=n+1&&ny<=n+1&&!vis[nx][ny]&&a[nx][ny]==0){
                vis[nx][ny]=1;
                q.push({nx,ny});
            }
        }
    }
}
int main(){
    cin>>n;
    for(int i=1;i<=n;i++){
        for(int j=1;j<=n;j++){
            cin>>a[i][j];
        }
    }
    BFS(0,0);
    for (int i=1;i<=n;i++) {
        for (int j=1;j<=n;j++) {
            if (a[i][j] == 0 &&!vis[i][j]) {
                cout<<2<<" ";
            }
            else cout<<a[i][j]<<" ";
        }
        cout<<'\n';
    }
    return 0;
}