九度·oj 1459

题目描述：

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.

输入：

n (1 < n < 17).

输出：

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.

样例输入：

68

样例输出：

Case 1:1 4 3 2 5 61 6 5 2 3 4Case 2:1 2 3 8 5 6 7 41 2 5 8 3 4 7 61 4 7 6 5 8 3 21 6 7 4 3 8 5 2

提示：

用printf打印输出。

#include<stdio.h>#include<string.h>#define true 1#define false 0using namespace std;int ans[22];int n;bool hash[22];int prime[]={2,3,5,7,11,13,17,19,23,29,31,37,41};bool judge(int x){     for(int i=0;i<13;i++)     {             if(prime[i]==x)             {                            return true;                            }                            }                            return false;                                                        }                            void check()                            {                                 if(judge(ans[n]+ans[1])==false)                                 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])==false)                                                               {                                                                                                return;                                                                                                }                                                                                                }                                                                                                if(num==n)                                                                                                {                                                                                                          check();                                                                                                          return;                                                                                                          }                                                                                                          for(int i=2;i<=n;i++)                                                                                                          {                                                                                                                  if(hash[i]==false)                                                                                                                  {                                                                                                                                hash[i]=true;                                                                                                                                ans[num+1]=i;                                                                                                                                DFS(num+1);                                                                                                                                hash[i]=false;                                                                                                                                }                                                                                                                                }                                                                                                                                }                                                                                                                                                                                                                                                                int main()                                                                                                                                {                                                                                                                                    int cas=0;                                                                                                                                    while(scanf("%d",&n)!=EOF)                                                                                                                                         {                     cas++;                                                                                                                                                              for(int i=0;i<22;i++)                                                                                                                                                              {                                                                                                                                                                      hash[i]=false;                                                                                                                                                                      }                                                                                                                                                                      ans[1]=1;                                                                                                                                                                      printf("Case %d:\n",cas);                                                                                                                                                                      hash[1]=true;                                                                                                                                                                      DFS(1);                                                                                                                                                                      printf("\n");                                                                                                                                                                      }                                                                                                                                                                      }