Contest1340/D.cpp

#include <bits/stdc++.h>
 
using namespace std;
int visit[41];
int prime[41];
int n;
int a[21];
int b[21];
int cut = 0;
int flag = 0;
 
void Prime() {
    //初始化都是素数
    for (int i = 2; i <= 40; i++) {
        if (!visit[i]) {
            prime[++prime[0]] = i;      //纪录素数， 这个prime[0] 相当于 cnt，用来计数
        }
        for (int j = 1; j <= prime[0] && i * prime[j] <= 40; j++) {
            visit[i * prime[j]] = 1;
            if (i % prime[j] == 0) {
                break;
            }
        }
    }
}
 
void dfs(int k) {
    if (cut == 1) {
        return;
    }
    if (k == n + 1 && visit[a[1] + a[n]] == 0) {
        for (int i = 1; i <= n; i++) {
            cout << a[i] << " ";
        }
        cout << endl;
        cut++;
    } else {
        for (int i = 1; i <= n; i++)   //***逐个尝试
        {
            if (b[i] == 0 && visit[i + a[k - 1]] == 0)  //***i没用过且满足条件
            {
                a[k] = i;    //***存储当前序列
                b[i] = 1;    //****标记
                dfs(k + 1);   //***递归
                b[i] = 0;    //***去除标记
            }
        }
    }
}
 
int main() {
    Prime();
    memset(a, 0, sizeof(a[0]));
    memset(b, 0, sizeof(b[0]));
    cin >> n;
    dfs(1);
    if (cut == 0) {
        cout << "no solution" << endl;
    }
    return 0;
}