题目1459：Prime ring problem(素数环问题——递归算法)

//
//  1459 Prime ring problem.cpp
//  Jobdu
//
//  Created by PengFei_Zheng on 23/04/2017.
//  Copyright © 2017 PengFei_Zheng. All rights reserved.
//

#include <stdio.h>
#include <iostream>
#include <algorithm>
#include <string.h>
#include <cmath>
#define PRIME 13
#define MAX_SIZE 21
using namespace std;

int n;
int ans[MAX_SIZE];
bool used[MAX_SIZE];

int prime[]={2,3,5,7,11,13,17,19,23,29,31,37,41};
bool judge(int x){
for(int i = 0 ; i < PRIME ; i++){
if(prime[i]==x)
return true;
}
return false;
}

void check(){
if(!judge(ans
+ans[1])) return;
for(int i = 1 ; i <= n ; i++){
if(i!=1) printf(" ");
printf("%d",ans[i]);
}
printf("\n");
}

void DFS(int num){
if(num>1){
if(!judge(ans[num] + ans[num - 1])) return;
}
if(num==n){
check();
return;
}
for(int i = 2 ; i <= n ; i++){
if(!used[i]){
used[i] = true;
ans[num+1] = i;
DFS(num+1);
used[i] = false;
}
}
}

int main(){
int kase = 0;
while(scanf("%d",&n)!=EOF){
kase++;
memset(used,false,sizeof(used));
ans[1] = 1;
used[1]=true;
printf("Case %d:\n",kase);
DFS(1);
printf("\n");
}
return 0;
}
/**************************************************************
Problem: 1459
User: zpfbuaa
Language: C++
Result: Accepted
Time:590 ms
Memory:1520 kb
****************************************************************/