Leetcode 94 Binary Tree Inorder

参考了这篇https://zxi.mytechroad.com/blog/tree/leetcode-94-binary-tree-inorder-traversal/

用到一个栈

cur = root ,cur初始指向根root

while 循环条件，只要cur不指向空，&& 栈不为空

　　cur 一路向左孩子指到底，并且压栈

　　到底了，弹出栈顶，将栈顶元素压入 res结果集即可。

　　再去指弹出元素的右孩子。

　　重复上述，只不过不是用递归的做法。用while循环来控制

代码

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

class Solution:
    def inorderTraversal(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
        if root is None:
            return []
        res = []
        stack = []
        cur = root
        while cur is not None or len(stack)>0:
            while cur is not None:
                stack.append(cur)
                cur = cur.left
            temp = stack.pop()
            res.append(temp.val)
            cur = temp
            cur = cur.right
        return res