SGU224 Little Queens（皇后问题模板题）

具体做法可参照Matrix67大牛的博客http://www.matrix67.com/blog/archives/266

#include<cstdio>
#include<string.h>
#include<iostream>
using namespace std;
int up,n,k,sum;
void test(int row,int ld,int rd,int cnt,int now)
{
    if(now>n)
    return;
    if(cnt<k)
    {
        int pos=up&(~(ld|rd|row));
        int p;
        while(pos)
        {
            p=pos&(-pos);
            pos=pos-p;
            test(row+p,(ld+p)<<1,(rd+p)>>1,cnt+1,now+1);
        }
        test(row,ld<<1,rd>>1,cnt,now+1);
    }
    else
    sum++;
}
int main()
{
    while(~scanf("%d%d",&n,&k))
    {
        up=(1<<n)-1;
        sum=0;
        test(0,0,0,0,0);
        printf("%d\n",sum);
    }
    return 0;
}