Example: C++ Heap Sort Implementation in C++

// C++ Heap Sort Implementation
#include <iostream>
#include <vector>
#include <algorithm> // Required for std::swap

// Function to heapify a subtree rooted with node i
// n is the size of the heap
void heapify(std::vector<int>& arr, int n, int i) {
    int largest = i;       // Initialize largest as root
    int left = 2 * i + 1;  // left child
    int right = 2 * i + 2; // right child

    // If left child is larger than root
    if (left < n && arr[left] > arr[largest]) {
        largest = left;
    }

    // If right child is larger than current largest
    if (right < n && arr[right] > arr[largest]) {
        largest = right;
    }

    // If largest is not root
    if (largest != i) {
        std::swap(arr[i], arr[largest]);

        // Recursively heapify the affected sub-tree
        heapify(arr, n, largest);
    }
}

// Main function to perform Heap Sort
void heapSort(std::vector<int>& arr) {
    int n = arr.size();

    // Step 1: Build a max-heap (rearrange array)
    // Start from the last non-leaf node and heapify upwards.
    for (int i = n / 2 - 1; i >= 0; i--) {
        heapify(arr, n, i);
    }

    // Step 2: Extract elements one by one from heap
    for (int i = n - 1; i > 0; i--) {
        // Move current root to end
        std::swap(arr[0], arr[i]);

        // Call max heapify on the reduced heap
        heapify(arr, i, 0);
    }
}

// Function to print an array
void printArray(const std::vector<int>& arr) {
    for (int x : arr) {
        std::cout << x << " ";
    }
    std::cout << std::endl;
}

int main() {
    // Example 1
    std::vector<int> arr1 = {12, 11, 13, 5, 6, 7};
    std::cout << "Original array 1: ";
    printArray(arr1);
    
    heapSort(arr1);
    
    std::cout << "Sorted array 1: ";
    printArray(arr1);

    std::cout << "--------------------" << std::endl;

    // Example 2
    std::vector<int> arr2 = {4, 10, 3, 5, 1};
    std::cout << "Original array 2: ";
    printArray(arr2);
    
    heapSort(arr2);
    
    std::cout << "Sorted array 2: ";
    printArray(arr2);

    return 0;
}