求助大佬，这个深搜写的问题在哪儿？我发现输出不出来（）

#include <iostream>
#include <cstring>
#include <cmath>
#include <algorithm>
using namespace std;
int n;
long long ans = 0;
int col[25],zx[30],yx[30];
int a[20];
void dfs(int x){      // x means which qz is put
    if(x > n){
        ans++;
        if(ans <= 3){
            for(int i = 1; i <= n ; ++i){
               cout << a[i] <<" ";               
            }
            cout << endl;
        }
        return;
    }
    for(int i = 1 ; i <= n ; ++i){
        if(col[i] == 0 && zx[abs(i + x)] == 0 && yx[abs(i - x)] == 0){
            a[x] = i;
            col[i] = 1; zx[abs(i + x)] = 1; yx[abs(i - x)] = 1;
            dfs(x + 1); 
            col[i] = 0; zx[abs(i - x)] = 0 ; yx[abs(i - x)] = 0;
        }
    }
}
int main()
{
    memset(col,0,sizeof(col));
    memset(zx,0,sizeof(zx));
    memset(yx,0,sizeof(yx));
    cin >> n;
    dfs(1);
    cout << ans << endl;
    return 0;
}