老早以前就遇到的一道题，那时候傻傻地用next_permutation()……dfs+剪枝

#include
using namespace std;
const int prime[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 vis[20],n,curr,p[20];
void dfs(int curr)
{
    if(curr==n&&prime[1+p[n-1]])
    {
        printf("1");
        for(int i=1;i