LeetCode -- Kth Smallest Element in a BST

/**
 * 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) 
 {
 	if(k < 1){
		return -1;
	}
 	var q = new Queue<int>();
    Inorder(root, q);
	
	int last = -1;
	for(var i = 0;i < k - 1; i++){
		if(q.Count > 0){
			last = q.Dequeue();
		}
	}
	
	return q.Count > 0 ? q.Dequeue() : last;
 }
 private void Inorder(TreeNode node, Queue<int> queue){
	if(node.left != null){
		Inorder(node.left, queue);
	}
	queue.Enqueue(node.val);
	if(node.right != null){
		Inorder(node.right, queue);
	}
	
 }
}

LeetCode -- Kth Smallest Element in a BST

原文：http://blog.csdn.net/lan_liang/article/details/48897017