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

include

include

include

include

include

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;
}