From 178846dd9872cf302de3a2fa7cab30d28a7e1dfd Mon Sep 17 00:00:00 2001
From: sarthakgupta1907-cell <sarthakgupta1907@gmail.com>
Date: Fri, 6 Nov 2026 11:11:36 +0530
Subject: [PATCH] feat: add array shuffle algorithm

---
 Data-Structures/Array/Shuffle.js           | 22 ++++++++++
 Data-Structures/Array/test/Shuffle.test.js | 47 ++++++++++++++++++++++
 2 files changed, 69 insertions(+)
 create mode 100644 Data-Structures/Array/Shuffle.js
 create mode 100644 Data-Structures/Array/test/Shuffle.test.js

diff --git a/Data-Structures/Array/Shuffle.js b/Data-Structures/Array/Shuffle.js
new file mode 100644
index 0000000000..01341a7a64
--- /dev/null
+++ b/Data-Structures/Array/Shuffle.js
@@ -0,0 +1,22 @@
+/**
+ * @function shuffle
+ * @description Randomly shuffles the elements of an array using the
+ *   Fisher-Yates (Knuth) shuffle algorithm.
+ * @param {Array} arr - The input array to shuffle
+ * @returns {Array} - A new shuffled array
+ * @see https://en.wikipedia.org/wiki/Fisher%E2%80%93Yates_shuffle
+ * @example shuffle([1, 2, 3, 4, 5]) => [3, 1, 5, 2, 4] (random order)
+ */
+const shuffle = (arr) => {
+  if (!Array.isArray(arr)) {
+    throw new TypeError('Input must be an array')
+  }
+  const result = [...arr]
+  for (let i = result.length - 1; i > 0; i--) {
+    const j = Math.floor(Math.random() * (i + 1))
+    ;[result[i], result[j]] = [result[j], result[i]]
+  }
+  return result
+}
+
+export { shuffle }
diff --git a/Data-Structures/Array/test/Shuffle.test.js b/Data-Structures/Array/test/Shuffle.test.js
new file mode 100644
index 0000000000..5c31065712
--- /dev/null
+++ b/Data-Structures/Array/test/Shuffle.test.js
@@ -0,0 +1,47 @@
+import { shuffle } from '../Shuffle.js'
+
+describe('shuffle', () => {
+  test('shuffle returns array of same length', () => {
+    expect(shuffle([1, 2, 3, 4, 5])).toHaveLength(5)
+  })
+
+  test('shuffle contains all original elements', () => {
+    const arr = [1, 2, 3, 4, 5]
+    const result = shuffle(arr)
+    expect(result.sort()).toEqual([...arr].sort())
+  })
+
+  test('shuffle empty array returns empty array', () => {
+    expect(shuffle([])).toEqual([])
+  })
+
+  test('shuffle single element returns same array', () => {
+    expect(shuffle([1])).toEqual([1])
+  })
+
+  test('shuffle does not mutate original array', () => {
+    const arr = [1, 2, 3, 4, 5]
+    shuffle(arr)
+    expect(arr).toEqual([1, 2, 3, 4, 5])
+  })
+
+  test('shuffle works with strings', () => {
+    const arr = ['a', 'b', 'c', 'd']
+    const result = shuffle(arr)
+    expect(result.sort()).toEqual([...arr].sort())
+  })
+
+  test('shuffle returns a new array', () => {
+    const arr = [1, 2, 3]
+    const result = shuffle(arr)
+    expect(result).not.toBe(arr)
+  })
+
+  test('throws TypeError for non-array input', () => {
+    expect(() => shuffle('123')).toThrow(TypeError)
+  })
+
+  test('throws TypeError for null input', () => {
+    expect(() => shuffle(null)).toThrow(TypeError)
+  })
+})