1261. Find Elements in a Contaminated Binary Tree

#### QUESTION:

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

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

#### SOLUTION:

/**
* Definition for a binary tree node.
* public class TreeNode {
*     int val;
*     TreeNode left;
*     TreeNode right;
*     TreeNode(int x) { val = x; }
* }
*/
class FindElements {
TreeNode root;

public FindElements(TreeNode root) {
this.root = root;
if (root != null) root.val = 0;
if (root.left != null)
FindElementsHelper(root.left, 0, true);
if (root.right != null)
FindElementsHelper(root.right, 0, false);
}

private void FindElementsHelper(TreeNode root,int value,boolean left){
if(left) root.val = 2*value+1;
else root.val = 2*value+2;
if (root.left != null)
FindElementsHelper(root.left, root.val, true);
if (root.right != null)
FindElementsHelper(root.right, root.val, false);
}

public boolean find(int target) {
return findHelper(target,root);
}

public boolean findHelper(int target,TreeNode node){
if(node.val == target) return true;
boolean left= false;
boolean right = false;
if(node.left!=null) left = findHelper(target,node.left);
if(node.right!=null) right = findHelper(target,node.right);
return left|right;
}
}

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