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?
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 inorder(self, root, k):
if root:
self.inorder(root.left, k)
self.i += 1
if self.i == k:
self.kth = root.val
self.inorder(root.right, k)
def kthSmallest(self, root: Optional[TreeNode], k: int) -> int:
self.i = 0
self.kth = None
self.inorder(root, k)
return self.kth
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