Q78- Rotates an array to the right by n positions in JavaScript

Rotating an array to the right means shifting elements towards the end, and elements that go past the last index wrap around to the front.

We can do this using arr.unshift().

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1️⃣ Using unshift and pop

• pop() removes the last element.
• unshift() adds one or more elements to the beginning of the array.

function rotateRight(arr, n) {
  n = n % arr.length; // handle n > arr.length

  for (let i = 0; i < n; i++) {
    let last = arr.pop();    // remove last element
    arr.unshift(last);       // add it to the front
  }

  return arr;
}

// Example
const array = [1, 2, 3, 4, 5];
console.log(rotateRight(array, 2)); // [4, 5, 1, 2, 3]

Explanation:

1. Remove last element using pop() → 5
2. Add it to front using unshift() → [5, 1, 2, 3, 4]
3. Repeat for n times → [4, 5, 1, 2, 3]

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2️⃣ Optimized Version Using Slice (Optional)

function rotateRightOptimized(arr, n) {
  n = n % arr.length;
  return arr.slice(-n).concat(arr.slice(0, arr.length - n));
}

console.log(rotateRightOptimized([1,2,3,4,5], 2)); // [4,5,1,2,3]

• arr.slice(-n) → last n elements
• arr.slice(0, arr.length - n) → rest of the elements
• concat() → combine them in rotated order

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⚡ Key Points About unshift

• Adds elements to the start of an array.
• Returns the new length of the array.
• Can be used with pop() to rotate arrays efficiently in small steps.

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In short:

To rotate an array to the right, repeatedly pop() the last element and unshift() it to the front, or use slicing for an optimized single-step rotation.