Leetcode - Kth Smallest Element in a BST

https://leetcode.com/problems/kth-smallest-element-in-a-bst/

Given a binary search tree, write a function kthSmallest to find the kth smallest element in it.

Note:
You may assume k is always valid, 1 ≤ k ≤ BST's total elements.

Example 1:

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

Inorder to trasversal the tree, and then find the k-th position.

/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func kthSmallest(root *TreeNode, k int) int {
    //count := 0
    stack := []*TreeNode{}
    node := root
    for node != nil || len(stack) != 0 {
        for node != nil {
            stack = append(stack, node)
            node = node.Left
        }
        if len(stack) != 0 {
            node = stack[len(stack)-1]
            k--
            if k == 0 {
                return node.Val
            }
            stack = stack[:len(stack)-1]
            node = node.Right
        }
    }
    return 0
}

• 相关文章
• 全局相关文章