Prime Ring Problem HDU - 1016

版权声明：仅供研究，转载请注明出处。 https://blog.csdn.net/CSUstudent007/article/details/82562690

 经典回溯法。。。

#include<iostream>
#include<cstring>
#include<string>
#include<cstdio>
#include<algorithm>
#include<cmath>
using namespace std;
int n;
int a[25];
bool vis[25];
bool check(int a){
	int k=2;
	if(a==1||a==2) return 1;
	while(k<a){
		if(a%k==0){
			return 0;
		}
		k++;
	}
	return 1;
}
void dfs(int cur){
	if(cur==n&&check(a[0]+a[n-1])){
		for(int i=0;i<n-1;i++){
			cout<<a[i]<<" ";
		}
		cout<<a[n-1]<<endl; 
	} 
	else for(int i=2;i<=n;i++){
		if(!vis[i]&&check(a[cur-1]+i)){
				vis[i]=1;
				a[cur]=i;
				dfs(cur+1);
				vis[i]=0; 
			}
		}
}
int main(){
	int k=0;
	while(cin>>n){
		k++;
		cout<<"Case "<<k<<":"<<endl;
		memset(a,0,sizeof(a));
		memset(vis,0,sizeof(vis));
		a[0]=1;
		dfs(1);
		cout<<endl;
	}
	return 0;
}