Given a binary search tree, write a function kthSmallest
to find the kth
smallest element in it.
Note:
You may assume k is always valid, 1 ≤ k ≤ BST's total elements.
Example 1:
Input: root = [3,1,4,null,2], k = 1 3 / \ 1 4 \ 2 Output: 1
Example 2:
Input: root = [5,3,6,2,4,null,null,1], k = 3 5 / \ 3 6 / \ 2 4 / 1 Output: 3
Follow up:
What if the BST is modified (insert/delete operations) often and you need to find the kth
smallest frequently? How would you optimize the kthSmallest routine?