Cod sursa(job #3262645)

Utilizator Alexandru_cioAlexandru Ciobanica Alexandru_cio Data 11 decembrie 2024 09:09:29
Problema Pairs Scor 100
Compilator cpp-64 Status done
Runda Arhiva de probleme Marime 0.59 kb
#include <bits/stdc++.h>

using namespace std;

ifstream f("pairs.in");
ofstream g("pairs.out");

const int NMAX=1e6;
long long n,maxim,v[NMAX+1],fr[NMAX+1];

int main()
{
    f>>n;
    for(int i=1;i<=n;i++)
    {
        long long x;
        f>>x;
        fr[x]++;
        maxim=max(maxim,x);
    }
    for(int i=maxim;i>=1;i--)
    {
        for(int j=1;j*i<=maxim;j++)
        {
            v[i]+=fr[j*i];
        }
        v[i]=v[i]*(v[i]-1)/2;
        for(int j=2;j*i<=maxim;j++)
        {
            v[i]-=v[j*i];
        }
    }
    g<<v[1];
    return 0;
}