翻了翻题解，都是用全局变量统计答案，那么以下是使用局部变量统计答案的做法，其实差不多

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>

using namespace std;

const int N = 10;

int n, m, t, x, y;
bool vis[N][N];
int dx[8] = {-2, -1, 1, 2, 2, 1, -1, -2};
int dy[8] = {1, 2, 2, 1, -1, -2, -2, -1};

int dfs(int x, int y, int cnt)
{
    if (cnt == n * m) {
        return 1;
    }
    int ans = 0;
    for (int i = 0; i < 8; i ++ )
    {
        int tx = x + dx[i], ty = y + dy[i];
        if (tx >= 0 && tx < n && ty >= 0 && ty < m) {
            if (vis[tx][ty]) continue;
            vis[tx][ty] = 1;
            ans += dfs(tx, ty, cnt + 1);
            vis[tx][ty] = 0;
        }

    }
    return ans;
}

int main(void) {
    scanf("%d", &t);
    while (t -- ) {
        scanf("%d%d%d%d", &n, &m, &x, &y);
        memset(vis, 0, sizeof vis);
        vis[x][y] = 1;
        cout << dfs(x, y, 1) << endl;
    }

    return 0;
}