Part 3.1 深度优先搜索

P1219 [USACO1.5] 八皇后 Checker Challenge

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;

int n, l[50], r[50], vis[50], a[50];
int ans;

void dfs(int x){
    if(x > n){
        if(ans < 3)for(int i = 1; i <= n; i++)cout << a[i] << ' ';
        if(ans < 3)cout << '\n';
        ans++;
    }
    for(int i = 1; i <= n; i++){
        if(l[i + x] || r[i - x + n] || vis[i])continue;
        l[i + x] = r[i - x + n] = vis[i] = 1;
        a[x] = i;
        dfs(x + 1);
        l[i + x] = r[i - x + n] = vis[i] = 0;
    }
}

void solve() {
    cin >> n;
    dfs(1);
    cout << ans;
}

int main() {
    ios::sync_with_stdio(false), cin.tie(0), cout.tie(0);
    int _ = 1; //cin >> _;
    while(_--) solve();
    return 0;
}