Add iterative version of Euclidean algorithm.

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…rithm/__test__/euclieanAlgorithm.test.js …ithm/__test__/euclideanAlgorithm.test.jssrc/algorithms/math/euclidean-algorithm/__test__/euclieanAlgorithm.test.js renamed to src/algorithms/math/euclidean-algorithm/__test__/euclideanAlgorithm.test.js src/algorithms/math/euclidean-algorithm/__test__/euclieanAlgorithm.test.js renamed to src/algorithms/math/euclidean-algorithm/__test__/euclideanAlgorithm.test.js

@@ -1,7 +1,7 @@
 import euclideanAlgorithm from '../euclideanAlgorithm';
 
 describe('euclideanAlgorithm', () => {
- it('should calculate GCD', () => {
+ it('should calculate GCD recursively', () => {
  expect(euclideanAlgorithm(0, 0)).toBe(0);
  expect(euclideanAlgorithm(2, 0)).toBe(2);
  expect(euclideanAlgorithm(0, 2)).toBe(2);

src/algorithms/math/euclidean-algorithm/__test__/euclideanAlgorithmIterative.test.js

@@ -0,0 +1,26 @@
+import euclideanAlgorithmIterative from '../euclideanAlgorithmIterative';
+
+describe('euclideanAlgorithmIterative', () => {
+ it('should calculate GCD iteratively', () => {
+ expect(euclideanAlgorithmIterative(0, 0)).toBe(0);
+ expect(euclideanAlgorithmIterative(2, 0)).toBe(2);
+ expect(euclideanAlgorithmIterative(0, 2)).toBe(2);
+ expect(euclideanAlgorithmIterative(1, 2)).toBe(1);
+ expect(euclideanAlgorithmIterative(2, 1)).toBe(1);
+ expect(euclideanAlgorithmIterative(6, 6)).toBe(6);
+ expect(euclideanAlgorithmIterative(2, 4)).toBe(2);
+ expect(euclideanAlgorithmIterative(4, 2)).toBe(2);
+ expect(euclideanAlgorithmIterative(12, 4)).toBe(4);
+ expect(euclideanAlgorithmIterative(4, 12)).toBe(4);
+ expect(euclideanAlgorithmIterative(5, 13)).toBe(1);
+ expect(euclideanAlgorithmIterative(27, 13)).toBe(1);
+ expect(euclideanAlgorithmIterative(24, 60)).toBe(12);
+ expect(euclideanAlgorithmIterative(60, 24)).toBe(12);
+ expect(euclideanAlgorithmIterative(252, 105)).toBe(21);
+ expect(euclideanAlgorithmIterative(105, 252)).toBe(21);
+ expect(euclideanAlgorithmIterative(1071, 462)).toBe(21);
+ expect(euclideanAlgorithmIterative(462, 1071)).toBe(21);
+ expect(euclideanAlgorithmIterative(462, -1071)).toBe(21);
+ expect(euclideanAlgorithmIterative(-462, -1071)).toBe(21);
+ });
+});

src/algorithms/math/euclidean-algorithm/euclideanAlgorithm.js

@@ -1,25 +1,15 @@
 /**
+ * Recursive version of Euclidean Algorithm of finding greatest common divisor (GCD).
  * @param {number} originalA
  * @param {number} originalB
  * @return {number}
  */
-
-/*Method 1: A bit Complex to understand*/
 export default function euclideanAlgorithm(originalA, originalB) {
+ // Make input numbers positive.
  const a = Math.abs(originalA);
  const b = Math.abs(originalB);
 
+ // To make algorithm work faster instead of subtracting one number from the other
+ // we may use modulo operation.
  return (b === 0) ? a : euclideanAlgorithm(b, a % b);
 }
-
-/*Method 2: Easy to evaluate*/
-export default function euclideanAlgorithm2(originalA, originalB) {
- const a = Math.abs(originalA);
- const b = Math.abs(originalB);
- 
- while(a != b){
- [a,b] = a>b : [a-b, b] : [a, b-a]
- }
- 
- return a || b;
-}

src/algorithms/math/euclidean-algorithm/euclideanAlgorithmIterative.js

@@ -0,0 +1,20 @@
+/**
+ * Iterative version of Euclidean Algorithm of finding greatest common divisor (GCD).
+ * @param {number} originalA
+ * @param {number} originalB
+ * @return {number}
+ */
+export default function euclideanAlgorithmIterative(originalA, originalB) {
+ // Make input numbers positive.
+ let a = Math.abs(originalA);
+ let b = Math.abs(originalB);
+
+ // Subtract one number from another until both numbers would become the same.
+ // This will be out GCD. Also quit the loop if one of the numbers is zero.
+ while (a && b && a !== b) {
+ [a, b] = a > b ? [a - b, b] : [a, b - a];
+ }
+
+ // Return the number that is not equal to zero since the last subtraction (it will be a GCD).
+ return a || b;
+}