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230. Kth Smallest Element in a BST (Medium)

Given the root of a binary search tree, and an integer k, return the kth smallest value (1-indexed) of all the values of the nodes in the tree.

 

Example 1:

Input: root = [3,1,4,null,2], k = 1
Output: 1

Example 2:

Input: root = [5,3,6,2,4,null,null,1], k = 3
Output: 3

 

Constraints:

  • The number of nodes in the tree is n.
  • 1 <= k <= n <= 104
  • 0 <= Node.val <= 104

 

Follow up: If the BST is modified often (i.e., we can do insert and delete operations) and you need to find the kth smallest frequently, how would you optimize?

Related Topics

[Tree] [Depth-First Search] [Binary Search Tree] [Binary Tree]

Similar Questions

  1. Binary Tree Inorder Traversal (Easy)
  2. Second Minimum Node In a Binary Tree (Easy)

Hints

Hint 1 Try to utilize the property of a BST.
Hint 2 Try in-order traversal. (Credits to @chan13)
Hint 3 What if you could modify the BST node's structure?
Hint 4 The optimal runtime complexity is O(height of BST).