230. Kth Smallest Element in a BST

这道题太简单了，利用BST的性质即可，不说了。
/**
* Definition for a binary tree node.
* public class TreeNode {
*     public int val;
*     public TreeNode left;
*     public TreeNode right;
*     public TreeNode(int x) { val = x; }
* }
*/
public class Solution {
public int KthSmallest(TreeNode root, int k) {
List<int> elems = new List<int>();
Traverse(root, elems);
return elems[k - 1];
}

private void Traverse(TreeNode root, List<int> elems)
{
if (root == null)
return;
if (root.left != null)
Traverse(root.left, elems);
elems.Add(root.val);
if (root.right != null)
Traverse(root.right, elems);
}
}