发题解喽

#include<bits/stdc++.h>
using namespace std;
struct node{
	int x, y;
};
int a[35][35];
bool vis[35][35];
int dir[4][2] = {-1, 0, 0, -1, 0, 1, 1, 0};
int n;
int check(int x, int y){
	if(x < 1 || x > n)
		return 1;
	if(y < 1 || y > n)
		return 2;
	if(a[x][y] == 1)
		return 3;
	if(vis[x][y])
		return 4;
	return 5;
}
void bfs(int x, int y){
	vector <node> v;
	v.push_back({x, y});
	bool flag = 1;
	for(int i = 0; i < v.size(); i++){
		node head = v[i];
		if(head.x == 1 || head.x == n || head.y == 1 || head.y == n) flag = 0;
		for(int j = 0; j < 4; j++){
			int xx = head.x + dir[j][0], yy = head.y + dir[j][1];
			if(check(xx, yy) == 5){
				vis[xx][yy] = 1;
				v.push_back({xx, yy});
			}
		}
	}
	if(flag)
		for(auto it:v)
			a[it.x][it.y] = 2;
}
int main(){
	cin >> n;
	for(int i = 1; i <= n; i++)
		for(int j = 1; j <= n; j++)
			cin >> a[i][j];
	for(int i = 1; i <= n; i++)
		for(int j = 1; j <= n; j++)
			if(a[i][j] == 0 && !vis[i][j])
				bfs(i, j);
	for(int i = 1; i <= n; i++){
		for(int j = 1; j <= n; j++)
			cout << a[i][j] << ' ';
		cout << endl;
	}
	return 0;
}