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1261. Find Elements in a Contaminated Binary Tree

Given a binary tree with the following rules:

  1. root.val == 0
  2. If treeNode.val == x and treeNode.left != null, then treeNode.left.val == 2 * x + 1
  3. If treeNode.val == 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.

You need to first recover the binary tree and then implement the FindElements class:

  • FindElements(TreeNode* root) Initializes the object with a contamined binary tree, you need to recover it first.
  • bool find(int target) Return if the target value exists in the recovered binary tree.

Example 1:

Input: ["FindElements","find","find"] [[[-1,null,-1]],[1],[2]] Output: [null,false,true] Explanation: FindElements findElements = new FindElements([-1,null,-1]); findElements.find(1); // return False findElements.find(2); // return True

Example 2:

Input: ["FindElements","find","find","find"] [[[-1,-1,-1,-1,-1]],[1],[3],[5]] Output: [null,true,true,false] Explanation: FindElements findElements = new FindElements([-1,-1,-1,-1,-1]); findElements.find(1); // return True findElements.find(3); // return True findElements.find(5); // return False

Example 3:

Input: ["FindElements","find","find","find","find"] [[[-1,null,-1,-1,null,-1]],[2],[3],[4],[5]] Output: [null,true,false,false,true] Explanation: FindElements findElements = new FindElements([-1,null,-1,-1,null,-1]); findElements.find(2); // return True findElements.find(3); // return False findElements.find(4); // return False findElements.find(5); // return True

Constraints:

  • TreeNode.val == -1
  • The height of the binary tree is less than or equal to 20
  • The total number of nodes is between [1, 10^4]
  • Total calls of find() is between [1, 10^4]
  • 0 <= target <= 10^6

Solutions (Python)

1. Solution

# Definition for a binary tree node.# class TreeNode:# def __init__(self, x):# self.val = x# self.left = None# self.right = NoneclassFindElements: def__init__(self, root: TreeNode): self.vals=set() root.val=0stack= [root] whilestack: curr=stack.pop() self.vals.add(curr.val) ifcurr.left: curr.left.val=2*curr.val+1stack.append(curr.left) ifcurr.right: curr.right.val=2*curr.val+2stack.append(curr.right) deffind(self, target: int) ->bool: returntargetinself.vals# Your FindElements object will be instantiated and called as such:# obj = FindElements(root)# param_1 = obj.find(target)
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