质因子

直接暴力枚举

C++ 代码

#include <bits/stdc++.h>
#define int long long
#define end '\n'
using namespace std;
const int N = 1e7 + 10;
int primes[N], cnt;
bool st[N];
inline void get(int x)
{
    for (int i = 2; i <= x; i ++ )
    {
        if (!st[i]) primes[cnt ++] = i;
        for (int j = 0; primes[j] * i <= x; i ++ )
        {
            st[primes[j] * i] = true;
            if (i % primes[j] == 0) break;
        }
    }
}
inline int solve()
{
    int n;
    cin >> n;
    int res = 1;
    for (int i = 0; i < cnt && primes[i] * primes[i] <= n; i ++ )
    {
        int p = primes[i];
        if (n % p == 0)
        {
            int s = 0;
            while (n % p == 0) n /= p, s ++;
            res *= (2 * s + 1);
        }
    }
    if (n > 1) res *= (2 * 1 + 1);
    return (res + 1) / 2;
}
signed main()
{
    int t = 1;
    cin >> t;
    get(N);
    for (int i = 1; i <= t; i ++)
    printf("Case %lld: %lld\n", i, solve());
    return 0;
}