How many prime numbers

Time Limit: 3000/1000 MS (Java/Others)    Memory Limit: 32768/32768 K (Java/Others)
Total Submission(s): 7120    Accepted Submission(s): 2375

Problem Description   Give you a lot of positive integers, just to find out how many prime numbers there are. Input   There are a lot of cases. In each case, there is an integer N representing the number of integers to find. Each integer won’t exceed 32-bit signed integer, and each of them won’t be less than 2. Output   For each case, print the number of prime numbers you have found out. Sample Input 3 2 3 4 Sample Output 2 Author wangye Source Recommend 威士忌 網上查了一下，這題要用相應的演算法解：miller_rabin演算法。學習下。。。
米勒拉賓素數測試，解大規模素數問題。

#include<iostream>
using namespace std ;
__int64 qpow(int a,int b,int r)
{
    __int64 ans=1,buff=a;
    while(b)
    {
        if(b&1)
            ans=(ans*buff)%r;
        buff=(buff*buff)%r;
        b>>=1;
    }
    return ans;
}
bool Miller_Rabbin(int n,int a)
{
    int r=0,s=n-1,j;
    if(!(n%a))
        return false;
    while(!(s&1))
    {
        s>>=1;
        r++;
    }
    __int64 k=qpow(a,s,n);
    if(k==1)
        return true;
    for(j=0;j<r;j++,k=k*k%n)
        if(k==n-1)
            return true;
    return false;
}
bool IsPrime(int n)
{
    int tab[5]={2,3,5,7};
    for(int i=0;i<4;i++)
    {
        if(n==tab[i])
            return true;
        if(!Miller_Rabbin(n,tab[i]))
            return false;
    }
    return true;
}
int main()
{
    int n;
    while(~scanf("%d",&n))
    {
        int ans=0,a;
        for(int i=0;i<n;i++)
        {
            scanf("%d",&a);
            if(IsPrime(a))
                ans++;
        }
        printf("%d\n",ans);
    }
    return 0;
}