Heap

Heap.java

import java.util.ArrayList;

public class Heap {
    private ArrayList<Integer> arr;

    public Heap() {
        arr = new ArrayList<>();
    }

    public Heap(int... values) {
        this();

        for (int v : values) {
            insert(v);
        }
    }

    private void heapUp(int index) {
        int parentIdx = (index - 1) / 2;

        if (arr.get(index) > arr.get(parentIdx)) {
            int temp = arr.get(index);
            arr.set(index, arr.get(parentIdx));
            arr.set(parentIdx, temp);

            heapUp(parentIdx);
        }
    }


    private void heapDown(int index) {
        int leftChildIndex = index * 2 + 1;
        int rightChildIndex = index * 2 + 2;
        int largerValueIndex = index;

        if (leftChildIndex < arr.size() && arr.get(leftChildIndex) > arr.get(largerValueIndex)) {
            largerValueIndex = leftChildIndex;
        }
        if (rightChildIndex < arr.size() && arr.get(rightChildIndex) > arr.get(largerValueIndex)) {
            largerValueIndex = rightChildIndex;
        }

        if (largerValueIndex != index) {
            int temp = arr.get(largerValueIndex);
            arr.set(largerValueIndex, arr.get(index));
            arr.set(index, temp);

            heapDown(largerValueIndex);
        }
    }

    public int size() {
        return arr.size();
    }

    public void insert(int... values) {
        for (int v : values) {
            arr.add(v);
            heapUp(arr.size() - 1);
        }
    }

    public int delete() {
        if (arr.size() == 0) throw new ArrayIndexOutOfBoundsException();

        int removed = arr.remove(0);

        if (arr.size() != 0)
            arr.add(0, arr.remove(arr.size() - 1));

        heapDown(0);
        return removed;
    }

    public void printArray() {
        arr.forEach(System.out::println);
    }