[tips]筛选特定区间内素数个数

#include<iostream>

using namespace std;

int main()
{
int n[123457];
n[1] = 0;
for (int i = 2; i < 123457; i++)//数组初始化
n[i] = 1;
for (int i = 2; i < 352; i++)//制作质数筛
for (int j = 2 * i; j < 123457; j += i)
n[j] = 0;

int x, y;
while (cin >> x >> y)
{
int count = 0;
for (int i = x; i <= y; i++)
{
if (n[i])
count++;
}
cout << count << endl;
}
return 0;
}