From 6ec0b96c12bb474fb4779790cf336b68dd44520d Mon Sep 17 00:00:00 2001
From: sarthakgupta1907-cell <sarthakgupta1907@gmail.com>
Date: Fri, 6 Nov 2026 11:02:49 +0530
Subject: [PATCH] feat: add array rotate algorithm

---
 Data-Structures/Array/Rotate.js           | 25 ++++++++++++
 Data-Structures/Array/test/Rotate.test.js | 49 +++++++++++++++++++++++
 2 files changed, 74 insertions(+)
 create mode 100644 Data-Structures/Array/Rotate.js
 create mode 100644 Data-Structures/Array/test/Rotate.test.js

diff --git a/Data-Structures/Array/Rotate.js b/Data-Structures/Array/Rotate.js
new file mode 100644
index 0000000000..f8298f5cdc
--- /dev/null
+++ b/Data-Structures/Array/Rotate.js
@@ -0,0 +1,25 @@
+/**
+ * @function rotate
+ * @description Rotates an array to the right by k positions.
+ *   Elements that fall off the end are placed at the beginning.
+ * @param {Array} arr - The input array
+ * @param {number} k - Number of positions to rotate right
+ * @returns {Array} - The rotated array
+ * @see https://en.wikipedia.org/wiki/Circular_shift
+ * @example rotate([1, 2, 3, 4, 5], 2) => [4, 5, 1, 2, 3]
+ * @example rotate([1, 2, 3], 1) => [3, 1, 2]
+ * @example rotate([1, 2, 3], 3) => [1, 2, 3]
+ */
+const rotate = (arr, k) => {
+  if (!Array.isArray(arr)) {
+    throw new TypeError('First argument must be an array')
+  }
+  if (!Number.isInteger(k)) {
+    throw new TypeError('Second argument must be an integer')
+  }
+  if (arr.length === 0) return []
+  const steps = ((k % arr.length) + arr.length) % arr.length
+  return [...arr.slice(arr.length - steps), ...arr.slice(0, arr.length - steps)]
+}
+
+export { rotate }
diff --git a/Data-Structures/Array/test/Rotate.test.js b/Data-Structures/Array/test/Rotate.test.js
new file mode 100644
index 0000000000..278a6bdf46
--- /dev/null
+++ b/Data-Structures/Array/test/Rotate.test.js
@@ -0,0 +1,49 @@
+import { rotate } from '../Rotate.js'
+
+describe('rotate', () => {
+  test('rotate([1,2,3,4,5], 2) returns [4,5,1,2,3]', () => {
+    expect(rotate([1, 2, 3, 4, 5], 2)).toEqual([4, 5, 1, 2, 3])
+  })
+
+  test('rotate([1,2,3], 1) returns [3,1,2]', () => {
+    expect(rotate([1, 2, 3], 1)).toEqual([3, 1, 2])
+  })
+
+  test('rotate([1,2,3], 3) returns [1,2,3]', () => {
+    expect(rotate([1, 2, 3], 3)).toEqual([1, 2, 3])
+  })
+
+  test('rotate([1,2,3], 0) returns [1,2,3]', () => {
+    expect(rotate([1, 2, 3], 0)).toEqual([1, 2, 3])
+  })
+
+  test('rotate with k larger than array length', () => {
+    expect(rotate([1, 2, 3], 4)).toEqual([3, 1, 2])
+  })
+
+  test('rotate with negative k rotates left', () => {
+    expect(rotate([1, 2, 3, 4, 5], -2)).toEqual([3, 4, 5, 1, 2])
+  })
+
+  test('rotate empty array returns empty array', () => {
+    expect(rotate([], 3)).toEqual([])
+  })
+
+  test('rotate single element returns same array', () => {
+    expect(rotate([1], 5)).toEqual([1])
+  })
+
+  test('rotate does not mutate original array', () => {
+    const arr = [1, 2, 3, 4, 5]
+    rotate(arr, 2)
+    expect(arr).toEqual([1, 2, 3, 4, 5])
+  })
+
+  test('throws TypeError for non-array input', () => {
+    expect(() => rotate('123', 2)).toThrow(TypeError)
+  })
+
+  test('throws TypeError for float k', () => {
+    expect(() => rotate([1, 2, 3], 1.5)).toThrow(TypeError)
+  })
+})