I have made an implementation of the Euclidean algorithm in Java, following the pseudocode shown below.

As far as my knowledge goes, I can't find a way of making this more efficient.

I have looked into other peoples implementations of this algorithm and there are a few which are slightly shorter, and some that use recursion.

The pseudocode:

function gcd(a, b)
    while b ≠ 0
       t := b
       b := a mod b
       a := t
    return a

My implementation:

import java.util.Scanner;
public class EuclideanAlgorithm {
    public static void main (String [] args) {
        int a, b;
        try(Scanner sc = new Scanner(System.in);) {
            System.out.print("Enter integer a: ");
            a = sc.nextInt();
            System.out.print("Enter integer b: ");
            b = sc.nextInt();
        long start = System.nanoTime();
        int answer = EuclideanAlgorithm(a, b);
        long stop = System.nanoTime();
        System.out.println("gcd = " + answer);
        System.out.println("Execution time: " + ((stop - start) / 1e+6) + "ms.");


    public EuclideanAlgorithm() {}; //Suppress default constructor

    private static int EuclideanAlgorithm(int a, int b) {
        int t;
        while (b != 0) {
            t = b;
            b = a % b;
            a = t;
        return a;

Is there a way to make this implementation more efficient, and would it have been more efficient to use recursion?


1 Answer 1


I believe this is as efficient as it gets, save for quickly detecting edge cases (a == 0 or a == b), which I think would be negligible anyway.

Recursion wouldn't be more efficient than iterative version. Functional languages can optimize recursion to the point where there's no difference, but I don't think Java excels at that and there's a performance penalty of adding new frames to the stack.

Recursion can make code clearer and more readable sometimes, but that's another story.

As a side note:

public EuclideanAlgorithm() {}; //Suppress default constructor

What's the purpose of this "suppression"?


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