👨‍🏫 题目地址

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