web/node.js

const LEAF = 0;
const UNARY = 1;
const BINARY = 2;

function nodeHeight(node) {
    if (node == null) {
        return -1;
    }
    return 1 + Math.max(nodeHeight(node.left), nodeHeight(node.right));
}

function nodeRank(node) {
    if (node == null) {
        return -1;
    }
    return node.rank;
}

function nodeDifference(node, parent) {
    if (parent === undefined) {
        parent = node != null ? node.parent : null;
    }
    return nodeRank(parent) - nodeRank(node);
}

function nodeDifferences(node) {
    let r = nodeRank(node);
    let left = null;
    let right = null;

    if (node != null) {
        left = node.left;
        right = node.right;
    }

    return [r - nodeRank(left), r - nodeRank(right)];
}

function rotateRight(x) {
    let parent = x.parent;
    let y = x.left;
    // let z = x.right;

    if (parent != null) {
        if (parent.left === x) {
            parent.left = y;
        } else {
            parent.right = y;
        }
    }

    x.left = y.right;
    if (x.left != null) {
        x.left.parent = x;
    }

    y.right = x;
    x.parent = y;
    y.parent = parent;

    return y;
}

function rotateLeft(x) {
    let parent = x.parent;
    // let y = x.left;
    let z = x.right;

    if (parent != null) {
        if (parent.left === x) {
            parent.left = z;
        } else {
            parent.right = z;
        }
    }

    x.right = z.left;
    if (x.right != null) {
        x.right.parent = x;
    }

    z.left = x;
    x.parent = z;
    z.parent = parent;

    return z;
}

function findParentNode(value, node, missing) {
    if (missing === undefined) {
        missing = true;
    }

    newNode = node

    while (newNode && (missing || newNode.value != value)) {
        node = newNode;
        if (value < node.value) {
            newNode = node.left;
        } else if (node.value < value) {
            newNode = node.right;
        } else {
            // same value
            return null;
        }
    }

    return node;
}

function nodeSearch(value, node) {
    while (node && node.value != value) {
        node = (value < node.value) ? node.left : node.right;
    }

    return node;
}

function nodeMinimum(node) {
    while (node.left != null) {
        node = node.left;
    }
    return node;
}

function nodeMaximum(node) {
    while (node.right != null) {
        node = node.right;
    }
    return node;
}

class Node {
    constructor(value, left, right, parent) {
        this.value = value;
        this.rank = 0;

        this.parent = parent || null;
        this.left = left || null;
        this.right = right || null;
    }

    type() {
        if (this.left != null && this.right != null) {
            return BINARY;
        }

        if (this.left != null || this.right != null) {
            return UNARY;
        }

        return LEAF;
    }

    serialize() {
        return `Node(value=${this.value}, rank = ${this.rank}, left=${this.left}, right=${this.right}, parent=${this.parent})`;
    }

    toString() {
        return `Node(value=${this.value}, rank=${this.rank})`;
    }

    promote() {
        this.rank++;
        return this;
    }

    demote() {
        this.rank--;
        return this;
    }
}