"""
Definition of TreeNode:
class TreeNode:
    def __init__(self, val):
        self.val = val
        self.left, self.right = None, None
"""


class Solution:
    """
    @param: root: param root: The root of the binary search tree
    @param: k1: An integer
    @param: k2: An integer
    @return: return: Return all keys that k1<=key<=k2 in ascending order
    """
    def searchRange(self, root, k1, k2):
        # write your code here

        result = []

        def helper(root, k1, k2):
            if not root:
                return

            if root.val > k1:
                helper(root.left, k1, k2)

            if root.val >= k1 and root.val <= k2:
                result.append(root.val)

            if root.val < k2:
                helper(root.right, k1, k2)

        helper(root, k1, k2)
        return result