给定一个二叉树，返回它的中序 遍历。示例:输入: [1,null,2,3]1\2/3输出: [1,3,2]

代码

/*** Definition for a binary tree node.* public class TreeNode {*     int val;*     TreeNode left;*     TreeNode right;*     TreeNode(int x) { val = x; }* }*/
class Solution {List<Integer> res=new ArrayList<>();public List<Integer> inorderTraversal(TreeNode root) {getInorderTraversal(root);return res;}public void getInorderTraversal(TreeNode root) {if(root==null) return;getInorderTraversal(root.left);res.add(root.val);getInorderTraversal(root.right);}
}