为什么vs2022能跑，洛谷就不行……

#include <iostream>
#include <cmath>
#include <cstring>
using namespace std;

const int N = 20;

int cx[8] = { 1,1,1,0,0,-1,-1,-1 }, cy[8] = { 1,-1,0,-1,1,0,1,-1 };
int c = 0, select[N][N]{}, a[N][N]{};

static void matrix(int x, int y, int p, int n, int m)
{
	if (y >= m)
	{
		y = 0;
		x++;
	}
	if (x >= n)
	{
		c = max(c, p);
		return;
	}
	if (select[x][y] == 0)
	{
		for (int i = 0; i < 8; i++)select[x + cx[i]][y + cy[i]]++;
		matrix(x, y + 2, p + a[x][y], n, m);
		for (int i = 0; i < 8; i++) select[x + cx[i]][y + cy[i]]--;
	}
	matrix(x, y + 1, p, n, m);
	return;
}

int main()
{
	int T, n, m;
	cin >> T;
	while (T--)
	{
		cin >> n >> m;
		for (int i = 0; i < n; i++) for (int j = 0; j < m; j++) cin >> a[i][j];
		memset(select, 0, sizeof(select));
		c = 0;
		matrix(0, 0, 0, n, m);
		cout << c << endl;
	}

	return 0;
}