LeetCode-Binary Tree Inorder Traversal

题目：https://oj.leetcode.com/problems/binary-tree-inorder-traversal/

Given a binary tree, return the inorder traversal of its nodes' values.

For example:
Given binary tree {1,#,2,3},

   1    \     2    /   3

return [1,3,2].

Note: Recursive solution is trivial, could you do it iteratively?

confused what "{1,#,2,3}" means? > read more on how binary tree is serialized on OJ.

源码：Java版本
算法分析：使用栈。时间复杂度O(n)，空间复杂度O(n)

/** * Definition for binary tree * public class TreeNode { *     int val; *     TreeNode left; *     TreeNode right; *     TreeNode(int x) { val = x; } * } */public class Solution {    public List<Integer> inorderTraversal(TreeNode root) {        List<Integer> result=new ArrayList<Integer>();        Stack<TreeNode> stack=new Stack<TreeNode>();        TreeNode node=root;        do {            while(node!=null) {                stack.push(node);                node=node.left;            }                    if(!stack.isEmpty()) {                node=stack.pop();                result.add(node.val);                node=node.right;            }         }while(!stack.isEmpty() || node!=null);                return result;    }}