蒟蒻本来check用双重循环，87分TLE1个，之后就有了下面的代码：

#include<iostream>
using namespace std;

int a[15],n,cnt = 0;
bool vis[15];
int c[15],z[15],f[15];

bool check()
{
    for (int i = 1;i <= n;i++)
    {
        c[a[i]]++;
        z[i - a[i] + n]++;
        f[i + a[i]]++;
    }
    for (int i = 1;i <= 2 * n;i++)
        if (c[i] > 1 || z[i] > 1 || f[i] > 1) return false;
    return true;
}

void dfs(int step)
{
    if (step > n)
    {
        if (cnt >= 3)
        {
            cnt++;
            return ;
            
        }
        for (int i = 1;i <= n;i++) cout << a[i] << ' ';
        cout << endl;
        cnt++;
        return ;
    }
    for (int i = 1;i <= n;i++)
    {
        if (vis[i]) continue;
        a[step] = i;
        if (!check()) continue;
        vis[i] = true;
        dfs(step + 1);
        vis[i] = false;
        a[step] = 0;
    }
}

int main()
{
    cin >> n;
    dfs(1);
    cout << cnt << endl;
    return 0;
}

一重循环WA，悬关求调