Cod sursa(job #2494335)

Utilizator bigmixerVictor Purice bigmixer Data 17 noiembrie 2019 18:23:38
Problema Invers modular Scor 20
Compilator cpp-64 Status done
Runda Arhiva educationala Marime 1.34 kb
#include <bits/stdc++.h>
#define ll long long
#define all(a) (a).begin(), (a).end()
//#pragma GCC optimize("O3")
//#pragma GCC optimize("Ofast")
//#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#define sz() size()
#define fr first
#define sc second
#define pb push_back
#define er erase
#define in insert
#define pi pair<int,int>
#define pii pair<pair<int,int>,int>
#define mp make_pair
#define int long long
#define rc(s) return cout<<s,0
#define rcc(s) cout<<s,exit(0)
///#define cin fin
///#define cout fout
using namespace std;

const int mod=1e9+7;

int a,n;

int phi(int x){
    int rs=x;
    for(int i=2LL;i*i<=x;i++){
        if(x%i==0LL){
            rs=(rs/i)*(i-1LL);
            while(x%i==0LL) x/=i;
        }
    }
    if(x>=2LL) rs=((rs/x)*(x-1LL));
    return rs;
}

int lgp(int a,int b){
    if(b==0LL) return 1LL;
    else if(b==1LL) return a%n;
    else{
        int cc=(lgp(a,b/2LL)%n);
        if(b%2LL==1LL) return (cc%n)*(cc%n)*(a%n);
        else return (cc%n)*(cc%n);
    }
}

int32_t main(){
	//ios_base::sync_with_stdio(false);cin.tie(0);cerr.tie(0);cout.tie(0);
    srand(chrono::steady_clock::now().time_since_epoch().count());
    ifstream fin("inversmodular.in");
    ofstream fout("inversmodular.out");
    fin >> a >> n;
    fout << lgp(a,phi(n)-1LL)%n;
}