1016：Prime Ring Problem

Problem Description A ring is compose of n circles as shown in diagram. Put natural number 1, 2, ..., n into each circle separately, and the sum of numbers in two adjacent circles should be a prime. Note: the number of first circle should always be 1.  

 

Input n (0 < n < 20).  

 

Output The output format is shown as sample below. Each row represents a series of circle numbers in the ring beginning from 1 clockwisely and anticlockwisely. The order of numbers must satisfy the above requirements. Print solutions in lexicographical order. You are to write a program that completes above process. Print a blank line after each case.  

 

Sample Input 6 8  

 

Sample Output Case 1: 1 4 3 2 5 6 1 6 5 2 3 4 Case 2: 1 2 3 8 5 6 7 4 1 2 5 8 3 4 7 6 1 4 7 6 5 8 3 2 1 6 7 4 3 8 5 2

 

代码：（虽然不知道为什么提交通过不了···还是贴上来了···希望明眼人明示···）

#include <stdio.h>#include<cstring>

int primelist[38] = {0,0,1,1,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,1,0,0,0,1,0,0,0,0,0,1,0,1,0,0,0,0,0,1};  int a[10000];int visited[30];

int isPrime(int n){ if(primelist[n])  return 1; return 0;}

void primeCircle(int cur,int n){  if(cur==n&&isPrime(1+a[n-1])) {  for(int i=0;i<n-1;i++)   printf("%d ",a[i]);  printf("%d/n",a[n-1]); } else {   for(int i=2;i<=n;i++)   if(isPrime(a[cur-1]+i)&&visited[i]==0)   {    a[cur]=i;    visited[i]=1;    primeCircle(cur+1,n);    visited[i]=0;   } }}

int main(){

 int n,num=1; a[0]=1; memset(visited,0,sizeof(visited)); visited[1]=1;

 while(scanf("%d",&n)==1) {  printf("case %d:/n",num++);  primeCircle(1,n);  printf("/n"); }

    return 0;}