heap sort steps code example

Example 1: heap sort

// @see https://www.youtube.com/watch?v=H5kAcmGOn4Q

function heapify(list, size, index) {
    let largest = index;
    let left = index * 2 + 1;
    let right = left + 1;
    if (left < size && list[left] > list[largest]) {
        largest = left;
    }
    if (right < size && list[right] > list[largest]) {
        largest = right;
    }
    if (largest !== index) {
        [list[index], list[largest]] = [list[largest], list[index]];
        heapify(list, size, largest);
    }
    return list;
}

function heapsort(list) {
    const size = list.length;
    let index = ~~(size / 2 - 1);
    let last = size - 1;
    while (index >= 0) {
        heapify(list, size, --index);
    }
    while (last >= 0) {
        [list[0], list[last]] = [list[last], list[0]];
        heapify(list, --last, 0);
    }
    return list;
}

heapsort([4, 7, 2, 6, 4, 1, 8, 3]);

Example 2: heap sort heapify and max heap in binary tree

Implementation of heap sort in C:

#include <stdio.h>
int main()
{
   int heap[10], array_size, i, j, c, root, temporary;
   printf("\n Enter size of array to be sorted :");
   scanf("%d", &array_size);
   printf("\n Enter the elements of array : ");
   for (i = 0; i < array_size; i++)
      scanf("%d", &heap[i]);
   for (i = 1; i < array_size; i++)
   {
       c = i;
       do
       {
           root = (c - 1) / 2;            
           if (heap[root] < heap[c])   /* to create MAX heap array */
           {                                  // if child is greater than parent swap them
               temporary = heap[root];      // as structure is of complete binary tree
               heap[root] = heap[c];     // it took logn steps to reach from root to leaf
               heap[c] = temporary;
           }
           c = root;
       } while (c != 0);
   }
   printf("Heap array : ");
   for (i = 0; i < array_size; i++)
       printf("%d\t ", heap[i]);         //printing the heap array
   for (j = array_size - 1; j >= 0; j--)
   {
       temporary = heap[0];
       heap[0] = heap[j] ;   /* swap max element with rightmost leaf element */
       heap[j] = temporary;
       root = 0;
       do
       {
           c = 2 * root + 1;    /* left node of root element */
           if ((heap[c] < heap[c + 1]) && c < j-1)
               c++;
           if (heap[root]<heap[c] && c<j)    /* again rearrange to max heap array */
           {
               temporary = heap[root];
               heap[root] = heap[c];
               heap[c] = temporary;
           }
           root = c;
       } while (c < j);
   }
   printf("\n The sorted array is : ");
   for (i = 0; i < array_size; i++)
      printf("\t %d", heap[i]);
}

Example 3: heap sort

# Heap Sort in python


  def heapify(arr, n, i):
      # Find largest among root and children
      largest = i
      l = 2 * i + 1
      r = 2 * i + 2
  
      if l < n and arr[i] < arr[l]:
          largest = l
  
      if r < n and arr[largest] < arr[r]:
          largest = r
  
      # If root is not largest, swap with largest and continue heapifying
      if largest != i:
          arr[i], arr[largest] = arr[largest], arr[i]
          heapify(arr, n, largest)
  
  
  def heapSort(arr):
      n = len(arr)
  
      # Build max heap
      for i in range(n//2, -1, -1):
          heapify(arr, n, i)
  
      for i in range(n-1, 0, -1):
          # Swap
          arr[i], arr[0] = arr[0], arr[i]
  
          # Heapify root element
          heapify(arr, i, 0)
  
  
  arr = [1, 12, 9, 5, 6, 10]
  heapSort(arr)
  n = len(arr)
  print("Sorted array is")
  for i in range(n):
      print("%d " % arr[i], end='')