Factors of Factorial---求N!的因子数量

Factors of Factorial - AtCoder arc067_a - Virtual Judge (vjudge.net)

比如36=2^2*3*2

约数个数是:(2+1)*(2+1)=9

然而此题需要求N!的因子个数，绝不可能算出N!

方法是只需要对2-N范围内分解质因数 存入数组 就可以

#include<iostream>
#include<algorithm>
#include<cstring>
#define int long long
using namespace std;
int a[10000001];
int n;	
int ans = 1; 
const int N = 1E9 + 7;
void solve()
{
	for (int i = 2; i <= n; i++)
	{
		int temp = i;//从2-N 
		for (int j = 2; j <= i; j++)
		{
			while (temp % j == 0)//分解质因数
			{
				a[j]++;
				temp /= j;
			}
		}
	} 
	for (int i = 2; i <= n; i++)
	{
		if (a[i]!=0)
		{
			ans *= (1 + a[i]);
			ans %= N;
		}
	}
	cout << ans % N << endl;
}
signed main()
{
	cin >> n;
	solve();
	return 0;

}