luogu1562 还是N皇后

题目

luogu1562

题解

这篇博客写的非常不错的 http://blog.csdn.net/Dora_Bin/article/details/52733832?locationNum=7

唉，位运算巨差，打了半个多小时，某C姓dalao秒A，果然还是要向强者多多学习

代码

#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <algorithm>
#define N 1000
using namespace std;

int n,ans,f[N],ed;
char mp[N][N],s[N];

void dfs(int x,int ld,int rd,int tot)
{
	if(x>n) {ans++;return;}
	int t=ed&~(ld|rd|tot|f[x]);
	while(t)
	{
		int p=t&(-t);
		dfs(x+1,(ld|p)>>1,(rd|p)<<1,tot|p);
		t-=p;
	}
}

int main()
{
	scanf("%d",&n);ed=(1<<n)-1;
	for(int i=1;i<=n;i++)
	{
		scanf("%s",s);
		int cnt=0;
		for(int j=0;j<n;j++)
			if(s[j]=='.') f[i]+=1<<j;
	}
	dfs(1,0,0,0);
	printf("%d",ans);
	return 0;
}