Check out example codes for "modular exponentiation c++". It will help you in understanding the concepts better.

Code Example 1

``````/**
* Calculate a^n in O(logn) time, instead of O(n) time with naive approach.
**/
public static long powerRecursive(int base, int exponent){
if(exponent == 0) return 1;
return (exponent % 2 == 0) ?
powerRecursive(base, exponent / 2) * powerRecursive(base, exponent / 2)
: base * powerRecursive(base, (exponent - 1) / 2) *
powerRecursive(base, (exponent - 1) / 2);
}``````

Code Example 2

``````// Iterative C++ program to compute modular power
#include <iostream>
using namespace std;

/* Iterative Function to calculate (x^y)%p in O(log y) */
int power(int x, unsigned int y, int p)
{
int res = 1;     // Initialize result

x = x % p; // Update x if it is more than or
// equal to p

if (x == 0) return 0; // In case x is divisible by p;

while (y > 0)
{
// If y is odd, multiply x with result
if (y & 1)
res = (res*x) % p;

// y must be even now
y = y>>1; // y = y/2
x = (x*x) % p;
}
return res;
}

// Driver code
int main()
{
int x = 2;
int y = 5;
int p = 13;
cout << "Power is " << power(x, y, p);
return 0;
}

// This code is contributed by shubhamsingh10``````

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