#include <bits/stdc++.h>
#pragma GCC optimize(2)
using namespace std;

int dx[5] = {0, -1, 0, 1, 0};
int dy[5] = {0, 0, 1, 0, -1};
int n, a[35][35];
bool vis[35][35];

int read()
{
	int sum = 0, w = 1;
    char ch = getchar();
    while (ch != '-' && !isdigit(ch))  ch = getchar();
    if (ch == '-')  w = -1, ch = getchar();
    while(isdigit(ch))  sum = (sum << 3) + (sum << 1) + ch - '0', ch = getchar();
    return sum * w;
}

bool check(int x, int y, bool f)
{
	if (a[x][y] == 1)  return 0;
	for (int i = 1; i <= 4; i++)
	{
		int tx = x + dx[i];
		int ty = y + dy[i];
		if (tx < 0 || ty < 0 || tx > n || ty > n)  return 0;
		if (!vis[tx][ty] && a[tx][ty] == 0)
		{
			vis[tx][ty] = 1;
			return check(tx, ty, 1);
			vis[tx][ty] = 0;
		}
	}
	if (!f)  return 1;
}

void fi(int x, int y)
{
	a[x][y] = 2;
	for (int i = 1; i <= 4; i++)
	{
		int tx = x + dx[i];
		int ty = y + dy[i];
		if (a[tx][ty] == 0)
			fi(tx, ty);
	}
}

int main()
{
    n = read();
    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 (check(i, j, 0))
			{
				fi(i, j);
				for (int k = 1; k <= n; k++)
				{
					for (int m = 1; m <= n; m++)
						cout << a[k][m] << " ";
					cout << endl;
				}
				exit(0);
			}
	return 0;
}

调试了半个小时还是没有发现什么错误，请求dalao们帮助