heap

#include <iostream>
using namespace std;
 
void heapify(int arr[], int n, int i) {
// Find largest among root, left child and right child
int largest = i;
int left = 2 * i + 1;
int right = 2 * i + 2;
 
if (left < n && arr[left] > arr[largest])
largest = left;
 
if (right < n && arr[right] > arr[largest])
largest = right;
 
// Swap and continue heapifying if root is not largest
if (largest != i) {
swap(arr[i], arr[largest]);
heapify(arr, n, largest);
}
}
 
// main function to do heap sort
void heapSort(int arr[], int n) {
// Build max heap
for (int i = n / 2 - 1; i >= 0; i--)
heapify(arr, n, i);
 
// Heap sort
for (int i = n - 1; i >= 0; i--) {
swap(arr[0], arr[i]);
 
// Heapify root element to get highest element at root again
heapify(arr, i, 0);
}
}
 
// Print an array
void printArray(int arr[], int n) {
for (int i = 0; i < n; ++i)
cout << arr[i] << " ";
cout << "\n";
}
 
// Driver code
int main() {
int arr[] = {1, 12, 9, 5, 6, 10};
int n = sizeof(arr) / sizeof(arr[0]);
heapSort(arr, n);
 
cout << "Sorted array is \n";
printArray(arr, n);