# 1261. Find Elements in a Contaminated Binary Tree
Given a binary tree with the following rules:
root.val == 0
If treeNode.val == x and treeNode.left != null, then treeNode.left.val == 2 * x + 1
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
# Solution
Approach 1: use a set to hold all values.
# Code (Python)
Approach 1:
class FindElements:
def __init__(self, root: TreeNode):
self.vals = set()
root.val = 0
stack = [root]
while stack:
node = stack.pop()
self.vals.add(node.val)
if node.left:
node.left.val = 2 * node.val + 1
stack.append(node.left)
if node.right:
node.right.val = 2 * node.val + 2
stack.append(node.right)
def find(self, target: int) -> bool:
return target in self.vals
# Code (C++)
Approach 1:
Approach 2: