八皇后 优化

 

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<string>
#include<cmath>
#include<set>
#include<vector>
#include<stack>
#include<queue>
#include<map>
using namespace std;
#define ll long long
#define se second
#define fi first
const int INF= 0x3f3f3f3f;
const int N=5e5+5;

int n,a[200],x1[200],x2[200],y[200],num=0; //x1,x2存的是对角线的情况

void dfs(int x)
{
    if(x>n){
        if(num<3){
            for(int i=1;i<=n;i++)
                cout<<a[i]<<' ';
            cout<<endl;
        }
        num++;
        return;
    }
    for(int i=1;i<=n;i++)
    {
        a[x]=i;
        if( !y[i] && !x1[x+i] && !x2[x-i+n])
        {
            y[i]=1;
            x1[x+i]=1;
            x2[x-i+n]=1;
            dfs(x+1);
            y[i]=0;
            x1[x+i]=0;
            x2[x-i+n]=0;
        }
    }
}

int main()
{
    cin>>n;
    dfs(1);
    cout<<num;
}