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:
Example 2:
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?
Solution
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, val=0, left=None, right=None):
# self.val = val
# self.left = left
# self.right = right
class Solution:
def kthSmallest(self, root: Optional[TreeNode], k: int) -> int:
def to_array(root: Optional[TreeNode]):
if not root:
return []
return to_array(root.left) + [root.val] + to_array(root.right)
return to_array(root)[k - 1]