經典回溯題

#include <cstdio>
#include <cstring>
#include <vector>
#include <queue>
#include <iostream>
#include <cmath>
#include <vector>
#include <algorithm>
#include <map>
using namespace std;
typedef long long ll;
#define DEBUG
const int maxn=1000+5,maxv=26
 
,INF=0x3f3f3f3f,mod=100000000;
bool isp[maxn],visited[maxn];
int A[maxn];
bool is_prime(int n){
    for(int i=2;i<=n/2;i++){
        if(n%i==0)return 0;
    }
    return 1;
}
void dfs(int cur,int n,int* A){
    if(cur==n&&isp[A[n-1]+A[0]]){
        for(int i=0;i<n;i++){
            printf("%d",A[i]);
            if
 
(i!=n-1)printf(" ");
        }
        printf("\n");
        return;
    }
    for(int i=2;i<=n;i++){
        if(visited[i])continue;
        if(!isp[i+A[cur-1]])continue;
        A[cur]=i;
        visited[i]=1;
        dfs(cur+1,n,A);
        visited[i]=0;
    }
}
int main(){
#ifdef DEBUG
    freopen("in.txt"
 
, "r", stdin);
    freopen("out.txt", "w", stdout);
#endif
    int n;
    int kase=0;
    while(cin>>n){
        if(kase)printf("\n");
        kase++;
        memset(visited,0,sizeof(visited));
        visited[1]=1;
        A[0]=1;
        for(int i=2;i<=2*n;i++)if(is_prime(i))isp[i]=1;
        printf("Case %d:\n", kase);
        dfs(1,n,A);

    }
#ifdef DEBUG
    fclose(stdin);
    fclose(stdout);
#endif
    return 0;
}