# What Is Heap Sort in Data Structure and Algorithm?

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Scott Campbell

Heap Sort is a popular sorting algorithm used in data structures and algorithms. It is an efficient and comparison-based algorithm that sorts a collection of elements in ascending or descending order. In this article, we will explore the working principle of Heap Sort and its implementation in detail.

## What is Heap Sort?

Heap Sort is based on the binary heap data structure, which is a complete binary tree that satisfies the heap property. The heap property ensures that each node in the binary tree has a value greater than or equal to (in a max heap) or less than or equal to (in a min heap) its child nodes.

Heap Sort works by first building a max heap from the given array of elements. Then, it repeatedly extracts the maximum element from the heap and places it at the end of the sorted array. This process continues until all elements are extracted and sorted.

## How Does Heap Sort Work?

The Heap Sort algorithm can be divided into two main steps:

• Build Max Heap: The first step involves building a max heap from the given array of elements. This is done by starting from the first non-leaf node (i.e., n/2 – 1) and performing a max-heapify operation on each node, moving upwards towards the root.

This ensures that every subtree rooted at any given node satisfies the heap property.

• Extract Max Element: Once we have built the max heap, we repeatedly extract the maximum element from it and place it at the end of the sorted array. After removing each element, we perform a max-heapify operation on the root node to maintain the heap property.

### Pseudocode for Heap Sort:

```function heapSort(array):
n = length(array)

// Build max heap
for i = n/2 - 1 to 0:
maxHeapify(array, n, i)

// Extract elements from heap one by one
for i = n-1 to 0:
swap array with array[i]
maxHeapify(array, i, 0)

function maxHeapify(array, size, root):
largest = root
left = 2 * root + 1
right = 2 * root + 2

if left < size and array[left] > array[largest]:
largest = left

if right < size and array[right] > array[largest]:
largest = right

if largest != root:
swap array[root] with array[largest]
maxHeapify(array, size, largest)
```

## Time Complexity of Heap Sort

The time complexity of Heap Sort is O(n log n), where n is the number of elements in the input array. This makes it an efficient sorting algorithm compared to other comparison-based algorithms like Bubble Sort and Insertion Sort. However, Heap Sort has a larger constant factor and requires additional memory space.

## Conclusion

Heap Sort is a powerful sorting algorithm that leverages the binary heap data structure. It provides an efficient way to sort a collection of elements in ascending or descending order. Although it may not be as intuitive as other sorting algorithms, understanding Heap Sort can be beneficial for solving complex problems efficiently.

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