import java.util.Arrays;
import java.util.InputMismatchException;
import java.util.Scanner;

public class HeapSort {

    // Function to perform heap sort
    public static void heapSort(int[] arr) {
        int n = arr.length;

        // 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
            int temp = arr[0];
            arr[0] = arr[i];
            arr[i] = temp;

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

    // To heapify a subtree rooted with node i which is an index in arr[]
    public static 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) {
            int swap = arr[i];
            arr[i] = arr[largest];
            arr[largest] = swap;

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

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        try {
            System.out.print("Enter the number of elements: ");
            int n = scanner.nextInt();
            if (n <= 0) {
                throw new IllegalArgumentException("Number of elements must be positive.");
            }

            int[] arr = new int[n];

            System.out.println("Enter the elements:");
            for (int i = 0; i < n; i++) {
                arr[i] = scanner.nextInt();
            }

            System.out.println("Original array: " + Arrays.toString(arr));

            heapSort(arr);

            System.out.println("Sorted array: " + Arrays.toString(arr));
        } catch (InputMismatchException e) {
            System.out.println("Invalid input. Please enter integers only.");
        } catch (IllegalArgumentException e) {
            System.out.println(e.getMessage());
        } finally {
            scanner.close();
        }
    }
}
