【USACO 1.5.2】特殊的质数肋骨

 1 #include <iostream>
 2 #include <cstdio>
 3 #include <cmath>
 4 #include <cstring>
 5 #include <algorithm>
 6 #include <queue>
 7 const int Max=10000000;
 8 using namespace std;
 9 int n,ans[Max],point=0;
10 void work(int num,int len);//len代表的数字的长度 
11 bool prime(int num);
12 int main()
13 {
14     //文件操作 
15     freopen("sprime.in","r",stdin);
16     freopen("sprime.out","w",stdout);
17     scanf("%d",&n); 
18     for (int i=1;i<=9;i++) 
19     if (prime(i)) work(i,1);
20     
21     sort(ans,ans+point);
22     for (int i=0;i<point;i++) printf("%d\n",ans[i]);
23     return 0;
24 }
25 bool prime(int num)
26 {
27      if (num==1) return 0;
28      if (num==2) return 1;
29      for (int i=2;i<=(int)sqrt((double)num)+1;i++) if (num%i==0) return 0;
30      return 1;
31 }
32 void work(int num,int len)
33 {
34      if (len>n) return;
35      if (len==n) {ans[point++]=num;return;}
36      for (int i=0;i<=9;i++)
37      if (prime(num*10+i)) work(num*10+i,len+1);
38 }