TYVJ P1080 N皇后

 1 #include<iostream>
 2 #include<cstdio>
 3 using namespace std;
 4 int n;
 5 int tar;
 6 int ans=0;
 7 int a[20];
 8 void dfs(int now,int la,int ra,int dep){
 9     if(now==tar){
10         ans++;
11         if(ans<=3){
12             for(int j=1;j<=n;j++)printf("%d ",a[j]);
13             printf("\n");
14         }
15         return;
16     }
17     int x=now|la|ra;
18     for(int i=0;i<n;i++){
19         if((x&(1<<i))==0){
20             a[dep]=i+1;
21             dfs(now|(1<<i),(la+(1<<i))<<1,(ra+(1<<i))>>1,dep+1);
22             
23         }
24     }
25 }
26 int main(){
27     scanf("%d",&n);
28     tar=(1<<n)-1;
29     for(int i=0;i<n;i++){
30         int pos=1<<i;
31         a[1]=i+1;
32         dfs(pos,pos<<1,pos>>1,2);
33     }
34     printf("%d\n",ans);
35     return 0;
36 }