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.
Input: root = [3,1,4,null,2], k = 1 Output: 1
Input: root = [5,3,6,2,4,null,null,1], k = 3 Output: 3
- The number of nodes in the tree is
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?
# 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 def inorder(root,res,k): if root==None:return heapq.heappush(res,-root.val) if len(res)>k:heapq.heappop(res) inorder(root.left,res,k) inorder(root.right,res,k) class Solution: def kthSmallest(self, root: TreeNode, k: int) -> int: res =  heapq.heapify(res) inorder(root,res,k) return -res