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 <= 1040 <= 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.
* type TreeNode struct {
* Val int
* Left *TreeNode
* Right *TreeNode
* }
*/
func kthSmallest(root *TreeNode, k int) int {
ans := 0
var helper func(*TreeNode)
helper = func(root *TreeNode){
if root == nil {
return
}
helper(root.Left)
k--
if k == 0 {
ans = root.Val
}
helper(root.Right)
}
helper(root)
return ans
}
Last modified 5mo ago