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

/**
 * 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
 */
const FindElements = function(root) {
  this.root = root
  this.set = new Set()
  if(root) this.set.add(0)
  
  dfs(root, 0, this.set)

  // console.log(this.set)
  function dfs(node, cur, set) {
    if(node == null) return
    
    if(node.left) {
      const child = cur * 2 + 1
      set.add(child)
      dfs(node.left, child, set)
    }
    if(node.right) {      
      const child = cur * 2 + 2
      set.add(child)
      dfs(node.right, child, set)
    }
  }
};

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


/** 
 * Your FindElements object will be instantiated and called as such:
 * var obj = new FindElements(root)
 * var param_1 = obj.find(target)
 */