getting_primefactors.cpp

#include<bits/stdc++.h>
#include<cmath>
#define _ ios_base::sync_with_stdio(false);cin.tie(NULL);cout.tie(NULL);
#define pb push_back
#define MAXN 10000
typedef long long llt;
typedef long double lld;
using namespace std;


int n;
int spf[MAXN];
void sieve()
{
    spf[1] = 1;
    for (int i=2; i<MAXN; i++)
        spf[i] = i;
    for (int i=4; i<MAXN; i+=2)
        spf[i] = 2;

    for (int i=3; i*i<MAXN; i++)
    {
        if (spf[i] == i)
        {
            for (int j=i*i; j<MAXN; j+=i)
                if (spf[j]==j)
                    spf[j] = i;
        }
    }
}

vector<int> getFactorization(int x)
{
    vector<int> ret;
    while (x != 1)
    {
        ret.push_back(spf[x]);
        x = x / spf[x];
    }
    return ret;
}