Find the lowest common ancestor of 2 nodes in a BST.

LowestCommonAncestor.js

class Relationship {
    constructor(root) {
        this.relObj = {}
        this.iterate(root, null, 0)
    }
    
    iterate(root, parent, level) {
        if (root) {
            this.relObj[root.val] = { level: level, parent: parent }
            this.iterate(root.left, root, level + 1)
            this.iterate(root.right, root, level + 1)
        }
    }
    
    getParent(node) {
        return (this.relObj[node.val] || {}).parent
    }
    
    getLevel(node) {
        return (this.relObj[node.val] || {}).level
    }
}

var moveQToPsLevel = function (p, q, rel) {
    let pLevel = rel.getLevel(p)
    let qLevel = rel.getLevel(q)
    while(qLevel > pLevel) {
        q = rel.getParent(q)
        qLevel = rel.getLevel(q)
    }
    return { p: p, q: q }
}

/**
 * Definition for a binary tree node.
 * function TreeNode(val) {
 *     this.val = val;
 *     this.left = this.right = null;
 * }
 */
/**
 * @param {TreeNode} root
 * @param {TreeNode} p
 * @param {TreeNode} q
 * @return {TreeNode}
 */
var lowestCommonAncestor = function(root, p, q) {
    var rel = new Relationship(root)
    let pLevel = rel.getLevel(p)
    let qLevel = rel.getLevel(q)
    if (pLevel < qLevel) {
        var newPQ = moveQToPsLevel(p, q, rel)
        p = newPQ.p
        q = newPQ.q
    } else if (pLevel > qLevel) {
        var newPQ = moveQToPsLevel(q, p, rel)
        p = newPQ.q
        q = newPQ.p
    }
    if (p.val === q.val) {
        return p
    } else {
        while(rel.getParent(p).val !== rel.getParent(q).val) {
            p = rel.getParent(p)
            q = rel.getParent(q)
        }
        return rel.getParent(p)
    }
};