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// @Title: 二叉搜索树中第K小的元素 (Kth Smallest Element in a BST)
// @Author: 15816537946@163.com
// @Date: 2021-10-17 20:08:18
// @Runtime: 12 ms
// @Memory: 6.3 MB
/**
 * Definition for a binary tree node.
 * type TreeNode struct {
 *     Val int
 *     Left *TreeNode
 *     Right *TreeNode
 * }
 */
func kthSmallest(root *TreeNode, k int) int {
    result := make([]int,0)
     var lnrtraversal func(*TreeNode)
    lnrtraversal = func(node *TreeNode) {
        if node == nil  {
            return 
        }

        if node.Left != nil {
            lnrtraversal(node.Left)
        }
        result = append(result, node.Val)

        if node.Right != nil {
            lnrtraversal(node.Right)
        }
        
    }
    
    lnrtraversal(root)

    return result[k-1]
}