187手写题解

#include <iostream>
#include <vector>
using namespace std;
const int N = 20;
int col[40], leftu[40], leftd[40];
int n, cnt;
vector<int> ans;
void dfs(int x) 
{
    if (x >= n + 1) 
    {
        cnt ++; 
        if (cnt <= 3) 
        { 
            for (int i = 0; i < ans.size(); i ++)
                cout << ans[i] << " ";
            cout << endl;
        }
    } 
    else 
    {
        for (int y = 1; y <= n; y ++) 
        {
            if (!col[y] && !leftu[x - y + 14] && !leftd[x + y]) 
            {
                col[y] = leftu[x - y + 14] = leftd[x + y] = 1; 
                ans.push_back(y);
                dfs(x + 1);
                col[y] = leftu[x - y + 14] = leftd[x + y] = 0;
                ans.pop_back();
            }
        }
    }
}
int main () 
{
    cin >> n;
    dfs(1); 
    cout << cnt << endl; 
    return 0;
}