leetcode - 两数之和Ⅳ 输入BST（653）

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def findTarget(self, root: TreeNode, k: int) -> bool:
        #先中序遍历 得到一个列表 
        tree_list = []
        def inOrder(root):
            if root == None:
                return None
            inOrder(root.left)
            tree_list.append(root.val)
            inOrder(root.right) 
        inOrder(root)
        #双指针
        i = 0
        j = len(tree_list)-1
        while(i<j):
            if (tree_list[i]+tree_list[j] == k):
                return True
            elif (tree_list[i]+tree_list[j] < k):
                i += 1
            else:
                j -= 1
        return False