Coding Challenge

Rotate the elements of an array by k positions to the right. Understand what the provided function does and determine the final output after rotation.

Task

Give this code a try and observe the results. Implement or analyze a function that rotates an array to the right by k steps without using external libraries, then determine what gets printed.

Formula

Normalize: k = ((k % n) + n) % n → Result: a.slice(-k).concat(a.slice(0, n - k))

Example Code


// Rotate an array to the right by k steps
const arr = [1, 2, 3, 4, 5];
const k = 2;

function rotateRight(a, k) {
  const n = a.length;
  // normalize k to avoid extra rotations and handle negatives
  k = ((k % n) + n) % n;
  // build the rotated array without mutating the original
  return a.slice(-k).concat(a.slice(0, n - k));
}

// What gets printed?
console.log(rotateRight(arr, k));

Question

What is the output of the console.log call above?

Options

[1, 2, 3, 4, 5]
[3, 4, 5, 1, 2]
[4, 5, 1, 2, 3]
[5, 1, 2, 3, 4]

Hint: Think about how negative indices in slice work and why normalizing k avoids unnecessary rotations.