HeapSort.java

import java.util.ArrayList;
import java.util.Arrays;

public class HeapSort {


    public static void main(String[] args) {
        int[] arr = {4, 5, 1, 6, 2, 7, 3, 8};
        sort(arr);
        System.out.println(Arrays.toString(arr));
    }

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

    public static void adjustHeap(int[] arr, int i, int length) {
        int temp = arr[i];
        for (int k = i * 2 + 1; k + 1 <= length; k = k * 2 + 1) {
            if (k + 1 < length && arr[k] < arr[k + 1]) {
                k++;
            }
            if (arr[k] > temp) {
                arr[i] = arr[k];
                i = k;
            } else {
                break;
            }
        }
        arr[i] = temp;
    }

    public static void swap(int[] arr, int a, int b) {
        int temp = arr[a];
        arr[a] = arr[b];
        arr[b] = temp;
    }


}