Merge pull request #34 from Chingye97/CollatSequence

tehliang · web-flow · commit a0bc0b99ae5f · 2022-08-31T13:33:35.000+08:00
Add CollatSequence.js
diff --git a/Maths/CollatzSequence.js b/Maths/CollatzSequence.js
@@ -0,0 +1,29 @@
+/**
+ * @function collatz
+ * @description Applies the Collatz Sequence on a specified number.
+ * The Collatz Sequence states that every natural number will always fall in a 1, 2, 4 loop when iterated under the following function:
+ * If the number is even, divide by 2, and if its odd, multiply it by 3 and add 1.
+ *
+ * @parama {Integer} n The number to apply the Collatz Sequence to.
+ *
+ * @return An array of steps and the final result..
+ *
+ * @see (Collatz Conjecture](https://en.wikipedia.org/wiki/Collatz_conjecture)
+ *
+ * @example collatz(1) = { result: 1, steps: [] }
+ * @example collatz(5) = { result: 1, steps: [16, 8, 4, 2, 1] }
+*/
+export function collatz (n) {
+  const steps = []
+  while (n !== 1) {
+    if (n % 2 === 0) {
+      n = n / 2
+    } else {
+      n = 3 * n + 1
+    }
+
+    steps.push(n)
+  }
+
+  return { result: n, steps: steps }
+}
diff --git a/Maths/test/CollatzSequence.test.js b/Maths/test/CollatzSequence.test.js
@@ -0,0 +1,8 @@
+import { collatz } from '../CollatzSequence'
+
+describe('The Collatz Sequence', () => {
+  it('Should be 1', () => {
+    expect(collatz(1)).toStrictEqual({ result: 1, steps: [] })
+    expect(collatz(5)).toStrictEqual({ result: 1, steps: [16, 8, 4, 2, 1] })
+  })
+})
