二叉树的中序遍历-python实现-Leetcode

递归和非递归方法中序遍历二叉树  Leetcode题

递归方法：

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

class Solution(object):
    def inorderTraversal(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
        ans = []
        if root==None:
            return ans
        self.inTraverse(root, ans)
        return ans
    def inTraverse(self, t, ans):
        if t.left:
            self.inTraverse(t.left, ans)
        ans.append(t.val)
        if t.right:
            self.inTraverse(t.right, ans)

非递归：

class Solution(object):
    def inorderTraversal(self, root):
        """
        :type root: TreeNode
        :rtype: List[int]
        """
    #     ans = []
    #     if root==None:
    #         return ans
    #     self.inTraverse(root, ans)
    #     return ans
    # def inTraverse(self, t, ans):
    #     if t.left:
    #         self.inTraverse(t.left, ans)
    #     ans.append(t.val)
    #     if t.right:
    #         self.inTraverse(t.right, ans)
    
        ans = []
        if root==None:
            return ans
        stack = []
        p = root
        while(p or len(stack)):
            if p:
                stack.append(p)
                p = p.left
            else:
                p = stack[-1]
                stack.pop(-1)
                ans.append(p.val)
                p = p.right
        return ans