94. 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].

递归喽

public class Solution {    public List<Integer> inorderTraversal(TreeNode root) {        List<Integer> result = new ArrayList<Integer>();        List<Integer> left = new ArrayList<Integer>();        List<Integer> right = new ArrayList<Integer>();        if (root == null) {            return result;        }        left = inorderTraversal(root.left);        right = inorderTraversal(root.right);        result.addAll(left);        result.add(root.val);        result.addAll(right);        return result;    }}