_heap.js

function maxHeapify(arr, n, i) {
  let largest = i;
  const left = 2 * i + 1;
  const right = 2 * i + 2;

  if (left < n && arr[left] > arr[largest]) {
    largest = left;
  }

  if (right < n && arr[right] > arr[largest]) {
    largest = right;
  }

  if (largest !== i) {
    [arr[i], arr[largest]] = [arr[largest], arr[i]];
    maxHeapify(arr, n, largest);
  }
}

function buildMaxHeap(arr) {
  const n = arr.length;
  const leaves = Math.floor(n / 2);
  for (let i = leaves - 1; i >= 0; i--) {
    maxHeapify(arr, n, i);
  }
}

function heapSort(arr) {
  const n = arr.length;
  buildMaxHeap(arr);

  for (let i = n - 1; i > 0; i--) {
    [arr[0], arr[i]] = [arr[i], arr[0]];
    maxHeapify(arr, i, 0);
  }
}

const arrayToSort = [12, 11, 13, 5, 6, 7];
heapSort(arrayToSort);
console.log(arrayToSort);