【USACO 1.5.1】回文质数

 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 long long a,b,ans[Max],point=0;
10 long long mi[15]={1,10,100,1000,10000,100000,1000000,10000000,100000000,1000000000,10000000000ll};
11 void work(long long num,long long len);//len代表的数字的长度 
12 bool prime(long long num);
13 int main()
14 {
15     //文件操作 
16     freopen("pprime.in","r",stdin);
17     freopen("pprime.out","w",stdout);
18     scanf("%lld%lld",&a,&b); 
19     for (long long i=0;i<=9;i++) 
20     {
21         work(i,1);
22         if (i!=0) work(i*10+i,2);
23     }
24     sort(ans,ans+point);
25     for (long long i=0;i<point;i++) printf("%lld\n",ans[i]);
26     return 0;
27 }
28 bool prime(long long num)
29 {
30      for (long long i=2;i<=(long long)sqrt((double)num)+1;i++) if (num%i==0) return 0;
31      return 1;
32 }
33 void work(long long num,long long len)
34 {
35 
36      if (num>b) return;
37      if (num>=a && prime(num)) ans[point++]=num;
38      for (long long i=1;i<=9;i++) 
39      for (long long j=1;j<=5;j++)
40      {
41          if ((len+j*2-1)<=10)
42          work(num*mi[j]+i+i*mi[len+j*2-1],len+j*2);
43      }
44 }