prime factorisation of a number in c 2b 2b

1// Function that returns a vector containing all the prime factors of n (25 --> 5, 5)
2vector<long long> prime_factorisation(long long n)
3{
4    //spf is smallest prime factor
5    map<long long, long long> spf;
6    vector<long long> ans(0);
7    for(long long i = 2; i <= n; i++) spf[i] = i;
8
9    for (long long i = 2; i <= n; i++)
10        if (spf[i] == i)
11            for (long long j = i * i; j <= n; j += i)
12                if (spf[j] == j)
13                    spf[j] = i;
14
15    while (n != 1)
16    {
17        ans.push_back(spf[n]);
18        n /= spf[n];
19    }
20    return ans;
21}