Heap sort

JavaScript, Algorithm, Array, Recursion · Dec 28, 2020

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;
};

heapsort([6, 3, 4, 1]); // [1, 3, 4, 6]

Written by Angelos Chalaris

I'm Angelos Chalaris, a JavaScript software engineer, based in Athens, Greece. The best snippets from my coding adventures are published here to help others learn to code.

If you want to keep in touch, follow me on GitHub or Twitter.

Heap sort

Written by Angelos Chalaris

More like this

Quick sort

Merge sort

Bucket sort