TheAlgorithms-C-Plus-Plus/modular_exponentiation

// Iterative C++ program for modular exponentiation.
//The program calculates the value of an integer raised to an integer exponent under modulo an integer.
#include <iostream> 


// Iterative Function to calculate a raised to exponent b under modulo c in O(log b) 
int power(int a, unsigned int b, int c) 
{ 
	int ans = 1;	    // Initialize the answer to be returned 

	a = a % c;          // Update a if it is more than or 
				        // equal to c 

	if (a == 0) 
	{
	    return 0;       // In case a is divisible by c; 
	}
	
	while (b > 0) 
	{ 
		// If b is odd, multiply a with answer 
		if (b & 1) 
		{
			ans = (ans*a) % c; 
		}
		
		// b must be even now 
		b = b>>1;       // b = b/2 
		a = (a*a) % c; 
	}
	
	return ans; 
} 

// Main Function
int main() 
{ 
	int num1 = 2; 
	int num2 = 5; 
	int m = 13; 
	std::cout << "The value of "<<num1<<" raised to exponent "<<num2<<" under modulo "<<m<<" is " << power(num1, num2, m); 
	return 0; 
}