Cod sursa(job #2663023)

Utilizator YusyBossFares Yusuf YusyBoss Data 25 octombrie 2020 09:45:54
Problema Invers modular Scor 100
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 0.87 kb
#include <iostream>
#include <stdio.h>

using namespace std;

int prod;

void rid_put(int x, int put, int mod) {
  if (put == 0)
    return;
  if (put % 2 == 1)
    prod = (1ll * prod * x) % mod;
  x = (1ll * x * x) % mod;
  rid_put(x, put / 2, mod);
}

int phi(int x) {
  int d, sol;

  sol = x;
  for (d = 2; d * d <= x; d++)
    if (x % d == 0) {
      while (x % d == 0)
        x /= d;
      sol = sol / d * (d - 1);
    }

  if (x > 1)
    sol = sol / x * (x - 1);
  return sol;
}

int inv_mod(int a, int n) {
  int nr = phi(n);
  prod = 1;
  rid_put(a, nr - 1, n);
  return prod;
}

int main() {
  FILE *fin, *fout;
  int a, n, nr;

  fin = fopen("inversmodular.in", "r");
  fscanf(fin, "%d%d", &a, &n);
  fclose( fin );

  fout = fopen("inversmodular.out", "w");
  fprintf(fout, "%d", inv_mod(a, n));
  fclose( fout );
  return 0;
}