Heap sort is a comparison-based sorting technique based on Binary Heap data structure. It is similar to selection sort where we first find the minimum element and place the minimum element at the beginning. We repeat the same process for the remaining elements.

Sorts an array of numbers, using the heapsort algorithm.

  • Use recursion.
  • Use the spread operator (...) to clone the original array, arr.
  • Use closures to declare a variable, l, and a function heapify.
  • Use a for loop and Math.floor() in combination with heapify to create a max heap from the array.
  • Use a for loop to repeatedly narrow down the considered range, using heapify and swapping values as necessary in order to sort the cloned array.
const heapsort = arr => {
  const a = [...arr];
  let l = a.length;

  const heapify = (a, i) => {
    const left = 2 * i + 1;
    const right = 2 * i + 2;
    let max = i;
    if (left < l && a[left] > a[max]) max = left;
    if (right < l && a[right] > a[max]) max = right;
    if (max !== i) {
      [a[max], a[i]] = [a[i], a[max]];
      heapify(a, max);
    }
  };

  for (let i = Math.floor(l / 2); i >= 0; i -= 1) heapify(a, i);
  for (i = a.length - 1; i > 0; i--) {
    [a[0], a[i]] = [a[i], a[0]];
    l--;
    heapify(a, 0);
  }
  return a;
};
Examples
heapsort([6, 3, 4, 1]); // [1, 3, 4, 6]