Example: Heap Sort for 5 Numbers in C++

// Heap Sort for 5 Numbers
#include <iostream>
#include <vector>
#include <algorithm> // For std::swap

// Function to heapify a subtree rooted with node i
// n is size of 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 largest so far
    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 do heap sort
void heapSort(std::vector<int>& arr, int n) {
    // Step 1: Build a max-heap (rearrange array)
    // Iterate from the last non-leaf node up to the root
    // (n/2 - 1) is the index of the last non-leaf node
    for (int i = n / 2 - 1; i >= 0; i--) {
        heapify(arr, n, i);
    }

    // Step 2: One by one extract an element from heap
    // After building the max-heap, the largest element is at the root (index 0).
    // Swap it with the last element of the heap, then reduce the heap size
    // and heapify the new root.
    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() {
    // Step 1: Define the array of 5 numbers
    std::vector<int> numbers = {4, 1, 3, 2, 5};
    int n = numbers.size();

    std::cout << "Original array: ";
    printArray(numbers);

    // Step 2: Apply heap sort
    heapSort(numbers, n);

    std::cout << "Sorted array: ";
    printArray(numbers);

    return 0;
}