Given a binary tree, return the inorder traversal of its nodes' values.
Example:
Input: [1,null,2,3]1\2/3Output: [1,3,2]
Follow up: Recursive solution is trivial, could you do it iteratively?
题意就是中序得出结果集，直接调用递归实现方法如下：
/**
* Definition for a binary tree node.
* public class TreeNode {
* int val;
* TreeNode left;
* TreeNode right;
* TreeNode(int x) { val = x; }
* }
*/
class Solution {
public List<Integer> inorderTraversal(TreeNode root) {
List<Integer> res = new ArrayList<>();
addRes(res,root);
return res;
}
public void addRes(List<Integer> res,TreeNode root) {
if(root==null) {
return;
}
addRes(res,root.left);
res.add(root.val);
addRes(res,root.right);
}
}