Kth Smallest Badge Number
A binary tree is given as a level-order array: tree[0] is the root, then the children of each real node are listed left to right, level by level. A missing child is written as null, and the children of a missing node are not listed at all. For example [1,2,3,null,4] is root 1 with children 2 and 3, where 2 has only a right child 4.
Employee badge numbers are stored in a binary search tree (left subtree smaller, right subtree larger, all distinct). Return the k-th smallest badge number, counting from 1.
An in-order walk visits the values in sorted order; stop as soon as you reach the k-th one.
Example 1
Input: tree = [3,1,4,null,2], k = 1 Output: 1 Explanation: Sorted order is 1, 2, 3, 4.
Example 2
Input: tree = [5,3,6,2,4,null,null,1], k = 3 Output: 3 Explanation: Sorted order is 1, 2, 3, 4, 5, 6.
Constraints
- 1 <= k <= number of nodes <= 10^4
- 1 <= node value <= 10^6
Hint 1
In-order traversal (left, node, right) of a BST yields sorted values.
Hint 2
Use an explicit stack so you can stop after k steps.
Good practice for: Backend Developer, Full Stack Developer, Database Administrator, Data Engineer, Cloud Engineer
Run checks your code on 3 sample tests. Submit runs all 8 tests, including hidden ones, and earns points. Use console.log to debug. Python's first run can take a few seconds while it starts.