Cod sursa(job #2456318)

Utilizator NeganAlex Mihalcea Negan Data 14 septembrie 2019 10:30:51
Problema Invers modular Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 0.74 kb
#include <fstream>

using namespace std;
ifstream fin("inversmodular.in");
ofstream fout("inversmodular.out");
int Phi(int n)
{
    int sol, p;
    sol = n;
    for(p = 2;n > 1 && p * p <= n;p++)
    {
        if(n % p == 0)
        {
            sol = sol / p * (p - 1);
            while(n % p == 0)
                n /= p;
        }
    }
    if(n > 1)
        sol = sol / n * (n - 1);
    return sol;
}
int invmod(int a, int n, int MOD)
{
    int sol = 1;
    while(n > 0)
    {
        if(n % 2 == 1)
            sol = 1LL * sol * a % MOD;
        n /= 2;
        a = 1LL * a * a % MOD;
    }
    return sol;
}
int a, n;

int main()
{
    fin >> a >> n;
    fout << invmod(a, Phi(n) - 1, n);
    return 0;
}