Computer Programming Contest Preparation

    1 #include <stdio.h>
    2 #include <math.h>
    3 
    4 #define MAX 19000000
    5 
    6 unsigned long long int list1[MAX],list2[MAX];
    7 int prime[MAX];
    8 void sieve_prime()
    9 {
   10     int i,j,k,l,m,count=0;
   11     unsigned long long int t=0;
   12     unsigned long long int serial;
   13     for(i=2; i<=MAX; i++)prime[i]=1;
   14     k=2;
   15     for(m=2; m<=sqrt(MAX); m++)
   16         {
   17             for(j=k+k; j<=MAX; j=j+k)
   18                 {
   19                     prime[j]=0;
   20 
   21                 }
   22             k++;
   23             for(; !prime[k]; k++);
   24         }
   25     for(i=0; i<=MAX; i++)
   26         {
   27             if(prime[i])
   28                 {
   29 
   30                     if(prime[i+2])
   31                         {
   32                             list1[t]=i;
   33                             list2[t]=i+2;
   34                             t++;
   35                         }
   36 
   37                 }
   38         }
   39 
   40 }
   41 
   42 int main()
   43 {
   44     sieve_prime();
   45     unsigned long long int serial,n1,n2,u,flag,count;
   46     while(scanf("%llu",&serial)==1&&serial!=0)
   47         {
   48 
   49             count=0;
   50             for(u=2; u<=serial/2; u++)
   51                 {
   52                     if(prime[u]==1 && prime[serial-u]==1)
   53                         {
   54 
   55                             count++;
   56                         }
   57 
   58                 }
   59             printf("%llu\n",count);
   60 
   61         }
   62 
   63     return 0;
   64 }
   65