1261-find-elements-in-a-contaminated-binary-tree.js

/**
 * 1261. Find Elements in a Contaminated Binary Tree
 * https://leetcode.com/problems/find-elements-in-a-contaminated-binary-tree/
 * Difficulty: Medium
 *
 * Given a binary tree with the following rules:
 * 1. root.val == 0
 * 2. For any treeNode:
 *   1. If treeNode.val has a value x and treeNode.left != null,
 *      then treeNode.left.val == 2 * x + 1
 *   2. If treeNode.val has a value x and treeNode.right != null,
 *      then treeNode.right.val == 2 * x + 2
 *
 * Now the binary tree is contaminated, which means all treeNode.val have
 * been changed to -1.
 *
 * Implement the FindElements class:
 * - FindElements(TreeNode* root) Initializes the object with a contaminated binary
 *   tree and recovers it.
 * - bool find(int target) Returns true if the target value exists in the recovered
 *   binary tree.
 */

/**
 * Definition for a binary tree node.
 * function TreeNode(val, left, right) {
 *     this.val = (val===undefined ? 0 : val)
 *     this.left = (left===undefined ? null : left)
 *     this.right = (right===undefined ? null : right)
 * }
 */
/**
 * @param {TreeNode} root
 */
var FindElements = function(root) {
  this.values = new Set();
  root.val = 0;

  const traverse = node => {
    if (!node) return;
    this.values.add(node.val);
    if (node.left) node.left.val = 2 * node.val + 1;
    if (node.right) node.right.val = 2 * node.val + 2;
    traverse(node.left);
    traverse(node.right);
  };

  traverse(root);
};

/**
 * @param {number} target
 * @return {boolean}
 */
FindElements.prototype.find = function(target) {
  return this.values.has(target);
};