Modular Exponentiation (Fast Power)

/*
 * Problem : Compute a^b mod m quickly.
 * Input   : Three integers a, b, m.
 * Output  : a^b mod m.
 * Approach: Square the base and halve the exponent.
 * Time    : O(log b)
 * Space   : O(1)
 * Java    : 8 or newer.
 */
import java.util.Scanner;

public class Main {
    // This method solves the task. It receives the input and returns the answer.
    static long solve(long a, long b, long m) {
        // Step 1: The result starts at 1. Keep the base smaller than m.
        long result = 1 % m;
        long base = a % m;
        long exponent = b;

        // Step 2: Repeat until the exponent is 0.
        while (exponent > 0) {
            // Step 3: If the exponent is odd, multiply the result by the base. Take mod after each multiplication.
            if (exponent % 2 == 1) {
                result = result * base % m;
            }

            // Step 4: Square the base and halve the exponent.
            base = base * base % m;
            exponent = exponent / 2;
        }
        return result;
    }

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        long a = scanner.nextLong();
        long b = scanner.nextLong();
        long m = scanner.nextLong();
        System.out.println(solve(a, b, m));
    }
}