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230. Kth Smallest Element in a BST

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Description

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?

Solutions

Python3

Java

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