HDU1016 dfs

刷回溯的时候发现我对DFS思路很不清晰，总是做着做着就乱了，刷个水题找找思路。

题意：经典DFS，找出所有的能让1~n的数形成素数环的序列（相邻相加为素数）；

 #include <iostream>
 #include <cmath>
 #include <cstdio>
 #include <cstring>
 #include <cstdlib>
 #include <string>
 #include <sstream>
 #include <algorithm>
 #define Max 2147483647
 #define INF 0x7fffffff
 #define ll long long
 #define mem(a,b) memset(a,b,sizeof(a))
 #define repu(i, a, b) for(int i = (a); i < (b); i++)
 const double PI=-acos(-1.0);
 #define N 10010
 using namespace std;
 bool pri[N];
 int p[N];
 int prim()
 {
     memset(pri, true, sizeof(pri));
     for(int i = ; i <= sqrt( +0.5); i++)
         if(pri[i])
             for(int j = i <<  ; j <= N; j += i)
                 pri[j] = false;
 }
 int n;
 bool vis[N];
 void dfs(int pos,int m)///p[pos-1] = m
 {
     if(pos == n+ && pri[p[n]+])
     {
         repu(i,,n)
         printf("%d ",p[i]);
         printf("%d\n",p[n]);
         return ;
     }
     int i = ;
     repu(i,,n+)
     {
         if(pri[m + i] && !vis[i] )///符合条件
         {
             vis[i] = ;
             p[pos] = i;
             dfs(pos+,p[pos]);
             vis[i] = ;
         }
     }
 }
 int main()
 {
     //init();
     prim();
     memset(vis,,sizeof(vis));
     int kase = ;
     while(~scanf("%d",&n))
     {
         printf("Case %d:\n",kase++);
         p[] = ;
         p[n+] = ;
         dfs(,);
         if(kase)
             printf("\n");
     }
     return ;
 }