USACO八皇后

VIS 0 1 2分别竖线和两个对角线，参见对角线(x,y)的和 差关系表

#include<iostream>
#include<cstdio>
#include<algorithm>
#include<cstring>
using namespace std;
const int N=;
int n,vis[][N<<],c[N],ans=;
void dfs(int cur){
    if(cur==n+){
        ans++;
        if(ans>) return;
        for(int i=;i<=n;i++) printf("%d ",c[i]); printf("\n");
        return;
    }
    for(int i=;i<=n;i++){
        if(!vis[][i]&&!vis[][i+cur]&&!vis[][cur-i+n]){
            vis[][i]=vis[][i+cur]=vis[][cur-i+n]=;
            c[cur]=i;
            dfs(cur+);
            vis[][i]=vis[][i+cur]=vis[][cur-i+n]=;
        }
    }
}
int main(){
    cin>>n;
    dfs();printf("%d",ans);
    return ;
}