Cod sursa(job #3225356)
Utilizator | Turcu Andrei and_ | Data | 17 aprilie 2024 13:45:29 |
---|---|---|---|
Problema | Pairs | Scor | 0 |
Compilator | cpp-64 | Status | done |
Runda | Arhiva de probleme | Marime | 0.6 kb |
#include <bits/stdc++.h>
using namespace std;
ifstream fin("pairs.in");ofstream fout("pairs.out");
const int N=100009;
int a[N],n,fr[N],ans[N];
int main()
{
fin >> n;
int ma=0;
for(int i=1;i<=n;i++)
{
fin >> a[i];
fr[ a[i] ]++;
ma=max(ma,a[i]);
}
for(int cm=ma;cm>=1;cm--) /// nr perechi de elem cu cmmdc = cm
{
for(int i=cm;i<=ma;i+=cm)
ans[cm]+=fr[i]; /// nr elemente
ans[cm] = ans[cm]*(ans[cm]-1)/2; /// nr perechi
for(int i=2*cm;i<=ma;i+=cm)
ans[cm]-=ans[i];
}
fout << ans[1];
return 0;
}