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