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C++ Program for Heap Sort
  • Difficulty Level : Medium
  • Last Updated : 27 Mar, 2019
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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 maximum element and place the maximum element at the end. We repeat the same process for remaining element.




// C++ program for implementation of Heap Sort
#include <iostream>
using namespace std;
  
// To heapify a subtree rooted with node i which is
// an index in arr[]. n is size of heap
void heapify(int arr[], int n, int i)
{
    int largest = i; // Initialize largest as root
    int l = 2 * i + 1; // left = 2*i + 1
    int r = 2 * i + 2; // right = 2*i + 2
  
    // If left child is larger than root
    if (l < n && arr[l] > arr[largest])
        largest = l;
  
    // If right child is larger than largest so far
    if (r < n && arr[r] > arr[largest])
        largest = r;
  
    // If largest is not root
    if (largest != i) {
        swap(arr[i], arr[largest]);
  
        // Recursively heapify the affected sub-tree
        heapify(arr, n, largest);
    }
}
  
// main function to do heap sort
void heapSort(int arr[], int n)
{
    // Build heap (rearrange array)
    for (int i = n / 2 - 1; i >= 0; i--)
        heapify(arr, n, i);
  
    // One by one extract an element from heap
    for (int i = n - 1; i >= 0; i--) {
        // Move current root to end
        swap(arr[0], arr[i]);
  
        // call max heapify on the reduced heap
        heapify(arr, i, 0);
    }
}
  
/* A utility function to print array of size n */
void printArray(int arr[], int n)
{
    for (int i = 0; i < n; ++i)
        cout << arr[i] << " ";
    cout << "\n";
}
  
// Driver program
int main()
{
    int arr[] = { 12, 11, 13, 5, 6, 7 };
    int n = sizeof(arr) / sizeof(arr[0]);
  
    heapSort(arr, n);
  
    cout << "Sorted array is \n";
    printArray(arr, n);
}
Output:
Sorted array is 
5 6 7 11 12 13

Please refer complete article on Heap Sort for more details!

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