剑指 二叉搜索树 第k小的结点

中序遍历 然后输出数组的k小结点

class Solution:
    # 返回对应节点TreeNode
    def KthNode(self, pRoot, k):
        # write code here
        result=[]
        def inorder(head):
            if not head:
                return 
            if head.left:
                inorder(head.left)
            result.append(head)
            if head.right:
                inorder(head.right)
        inorder(pRoot)
        if k>=1 and k<=len(result):
            return result[k-1]
        else:
            return None