【洛谷】P1219 [USACO1.5]八皇后 Checker Challenge

#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
int n, cnt = 0;
int idx[15], col[15], ud[30], ld[30];
void out(){
    cnt++;
    if (cnt <= 3){
        cout << idx[1];
        for (int i = 2; i <= n; i++) cout << " " << idx[i];
        cout <<endl;
    }
}
void dfs(int i){
    if (i > n){
        out();
        return;
    }
    for (int j = 1; j <= n; j++){
        if (!col[j] && !ud[i-j+n] && !ld[i+j]){
            idx[i] = j;
            col[j] = ud[i-j+n] = ld[i+j] = 1;
            dfs(i+1);
            col[j] = ud[i-j+n] = ld[i+j] = 0;
        }
    }
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout.tie(0);
//    freopen("in.txt", "r", stdin);
//    freopen("out.txt", "w", stdout);
    cin >> n;
    dfs(1);
    cout << cnt;
    return 0;
}