524:Prime Ring Problem

版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/qq_37754288/article/details/81713566

Prime Ring Problem

#include<bits/stdc++.h>
using namespace std;
const int maxn = 17;
int n;
int A[maxn],vis[maxn],p[2*maxn];
int isPrime(int n){
    for(int i = 2;i <= int(sqrt(n));i++){
        if(n % i == 0) return 0;
    }
    return 1;
}
void dfs(int cur){
    if(cur == n && p[A[0]+A[cur-1]]){
        for(int i = 0;i < n-1;i++){
            printf("%d ",A[i]);
        }
        printf("%d\n",A[n-1]);
    }
    for(int i = 2;i <= n;i++){
        if(!vis[i] && p[A[cur-1]+i]){
            A[cur] = i;
            vis[i] = 1;
            dfs(cur+1);
            vis[i] = 0;
        }
    }
}
int main()
{
    // freopen("data.in","r",stdin);
    // freopen("data.out","w",stdout);
    int kase = 0;
    for(int i = 1;i <= 2*maxn;i++){
        p[i] = isPrime(i);
    }
    while(scanf("%d",&n) != EOF){
        if(kase) putchar('\n');
        printf("Case %d:\n",++kase);
        A[0] = 1; vis[1] = 1;
        dfs(1);
    }
    return 0;
}