C++ Program for Heap Sort

// 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 Since we are using 0 based indexing
    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[] = { 60 ,20 ,40 ,70, 30, 10};
    int n = sizeof(arr) / sizeof(arr[0]);
  //heapify algorithm
  // the loop must go reverse you will get after analyzing manually 
  // (i=n/2 -1) because other nodes/ ele's are leaf nodes 
  // (i=n/2 -1) for 0 based indexing
  // (i=n/2)  for 1 based indexing
     for(int i=n/2 -1;i>=0;i--){
       heapify(arr,n,i);
   }
  
  cout << "After heapifying array is \n";
    printArray(arr, n);
  
  
    heapSort(arr, n);

    cout << "Sorted array is \n";
    printArray(arr, n);
    
  return 0;
}
//code by Prajwal Chougale

#include <algorithm>
#include <iostream>
#include <vector>
using namespace std;

void heapSort(int arr[], int n)
{
    // Convert array to vector
    vector<int> v(arr, arr + n);

    // Convert vector to Max Heap
    make_heap(v.begin(), v.end());

    // Sort Max Heap
    sort_heap(v.begin(), v.end());

    // Copy sorted vector back to array
    copy(v.begin(), v.end(), arr);
}

int main()
{
    int arr[] = { 60, 20, 40, 70, 30, 10 };
    int n = sizeof(arr) / sizeof(arr[0]);

    heapSort(arr, n);

    cout << "Sorted array is \n";
    for (int i = 0; i < n; ++i)
        cout << arr[i] << " ";
    cout << endl;
}