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