救救孩子

#include<iostream>
#include<algorithm>
#include<cstdio>
#include<queue>
using namespace std;
int dx[4]={0,0,1,-1};
int dy[4]={1,-1,0,0};
int a[40][40];
int n;
bool f[40][40];
int main(){
	cin>>n;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			cin>>a[i][j];
		}
	}
	queue<int> x;
	queue<int> y;
	x.push(0);
	y.push(0);
	while(!x.empty()){
		f[0][0]=1;
		for(int i=0;i<4;i++){
			int nx=x.front()+dx[i];
			int ny=y.front()+dy[i];
		    if(nx>=0&&ny<=n+1&&ny>=0&&ny<=n+1&&a[nx][ny]==0&&f[nx][ny]==0){
				f[nx][ny]=1;
				x.push(nx);
				y.push(ny);
		    }
		}
		x.pop();
		y.pop();
	}
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			if(a[i][j]==0&&f[i][j]==0){
				cout<<2<<" ";
			}
			else cout<<a[i][j]<<" ";
		}
		cout<<endl;
	}
	return 0;
}