K - How many prime numbers

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#K - How many prime numbers

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本文介绍了一种通过编程实现的素数计数方法。输入一系列正整数，算法将判断并统计其中的素数数量。核心部分使用了sqrt函数进行优化，避免了不必要的计算，提高了效率。

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K - How many prime numbers

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

#include <iostream>
#include <math.h>
#include <stdio.h>
using namespace std;

int xuan(int a)
{
    int i;
    int t=(int)sqrt(a);
    for(i=2; i<=t; i++)
    {
        if(a%i==0)
        {
            return 0;
        }
    }
    return 1;
}

int main()
{
    int a,b,i;
    int sum;
    while(scanf("%d",&a)!=EOF)
    {
        sum=0;
        for(i=1; i<=a; i++)
        {
            scanf("%d",&b);
            if(b==2)
            {
                sum=sum+1;
            }
            else
            {
                if(b%2==1)
                {
                    if(xuan(b)==1)
                    {
                        sum=sum+1;
                    }
                }
            }
        }
        cout << sum << endl;
    }
    return 0;
}