CPP

modular exponentiation algorithm c++

#include <iostream>
using namespace std;

int main()
{
    int b, n, m, x =1, a[10], i, k=0;
    int power;

    // input part
    cout<< "Enter base: ";
    cin>> b;

    cout<< "Enter power raised: ";
    cin>> n;

    cout<< "Enter modular value: ";
    cin>> m;

    power =  b % m;

    // converting value of n to binary
    for(i=0; n>0; i++)
    {
        a[i]=n%2;
        n= n/2;
        k++;
    }

    // getting value of x
    for(i=0; i<k; i++)
    {
        if (a[i] == 1)
        {
            x = (x * power) % m;
            power = (power * power) % m;
        }

        else
            power = (power * power) % m;
    }

    // x is the result of modular expansion (b^n mod m)
    cout<< x;

    return 0;
}