Lowest Common Ancestor of binary tree.md

Problem statement

Given a binary tree, find the lowest common ancestor (LCA) of two given nodes in the tree.

According to the definition of LCA on Wikipedia: “The lowest common ancestor is defined between two nodes p and q as the lowest node in T that has both p and q as descendants (where we allow a node to be a descendant of itself).”

/**
 * 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) {
    if (root === null || root === p || root === q) {
        return root;
    }

    const left = lowestCommonAncestor(root.left, p, q);
    const right = lowestCommonAncestor(root.right, p, q);

    if (left !== null && right !== null) {
        return root;
    }

    return left !== null ? left : right;
};