max-binary-heap.js

class MaxBinaryHeap {
    constructor () {
        this.values = [];
    }

    insert (value) {
        this.values.push(value);
        this.bubbleUp();
    }

    bubbleUp () {
        let index = this.values.length - 1;
        const element = this.values[index];

        while (index > 0) {
            const parentIndex = Math.floor((index - 1) / 2);
            const parent = this.values[parentIndex];
            if (parent >= element) break;
            this.values[parentIndex] = element;
            this.values[index] = parent;
            index = parentIndex;
        }

        return this;
    }

    extractMax () {
        const max = this.values[0];
        const end = this.values.pop();
        if (this.values.length > 0){
            this.values[0] = end;
            this.sinkDown();
        }
        return max;
    }

    sinkDown () {
        let parentIdx = 0;
        const parentElement = this.values[parentIdx];
        const length = this.values.length;
        while (true) {
            const leftChildIdx = 2 * parentIdx + 1;
            const rightChildIdx = 2 * parentIdx + 2;
            let leftChild = null;
            let rightChild = null;
            let swapIdx = null;

            if (leftChildIdx < length) {
                leftChild = this.values[leftChildIdx];
                if (leftChild > parentElement) {
                    swapIdx = leftChildIdx;
                }
            }

            if (rightChildIdx < length) {
                rightChild = this.values[rightChildIdx];
                if (
                    (swapIdx === null && rightChild > parentElement) ||
                    (swapIdx !== null && rightChild > leftChild)
                ) {
                    swapIdx = rightChildIdx;
                }
            }

            if (swapIdx === null) break;

            this.values[parentIdx] = this.values[swapIdx];
            this.values[swapIdx] = parentElement;
            parentIdx = swapIdx;
        }
    }
}

const MaxHeapify = (values) => {
    const maxHeap = new MaxBinaryHeap();

    for (const value of values) {
        maxHeap.insert(value);
    }

    return maxHeap;
};

const HeapSort = (values) => {
    const maxHeap = MaxHeapify(values);
    const result = [];

    while (maxHeap.values.length) {
        result.unshift(maxHeap.extractMax());
    }

    return result;
};

HeapSort([4,5,7,3,2,6,9,8]);