UVA - 524：Prime Ring Problem

Prime Ring Problem

来源：UVA

题目

A ring is composed of n (even number) circles as shown in diagram. Put natural numbers 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 (0 < n<=16)

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.
You are to write a program that completes above process.

输入样例

6
8

输出样例

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

参考代码

#include<cstdio>
int prime[]={2,3,5,7,11,13,17,19,23,29,31,37};
int arr[20],vis[20];
int n;bool is_prime(int num)
{for(int i=0;i<12;i++)if(prime[i]==num)return true;return false;
}
void dfs(int cur)
{if(cur==n && is_prime(arr[0]+arr[n-1])){for(int i=0;i<n;i++)printf("%d%c",arr[i],i==n-1?'\n':' ');}else for(int i=2;i<=n;i++){if(!vis[i] && is_prime(i+arr[cur-1])){arr[cur]=i;vis[i]=1;dfs(cur+1);vis[i]=0;}}
}
int main()
{int cnt=0;while(scanf("%d",&n)!=EOF){if(cnt)printf("\n");printf("Case %d:\n",++cnt);arr[0]=1;dfs(1);}return 0;
}

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UVA - 524：Prime Ring Problem

Prime Ring Problem

题目

输入

输出

输入样例

输出样例

参考代码

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