MaxHeap.java

import java.util.Scanner;

public class MaxHeap {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int T = scanner.nextInt();

        for (int i = 0; i < T; i++) {
            int N = scanner.nextInt();
            int[] arr = new int[N];

            for (int j = 0; j < N; j++) {
                arr[j] = scanner.nextInt();
            }

            buildMaxHeap(arr);

            for (int j = 0; j < N; j++) {
                System.out.print(arr[j] + " ");
            }
            System.out.println();
            scanner.close();
        }
    }

    public static void buildMaxHeap(int[] arr) {
        int n = arr.length;
        for (int i = n / 2 - 1; i >= 0; i--) {
            heapify(arr, n, i);
        }
    }

    public static void heapify(int[] arr, int n, int i) {
        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;
        }

        if (largest != i) {
            int temp = arr[i];
            arr[i] = arr[largest];
            arr[largest] = temp;

            heapify(arr, n, largest);
        }
    }
}