[코테 풀이] Binary Tree Inorder Traversal

Q_94) Binary Tree Inorder Traversal

출처 : https://leetcode.com/problems/binary-tree-inorder-traversal/

Given the root of a binary tree, return the inorder traversal of its nodes' values.

// *
//  * 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 {
    List<Integer> l = new ArrayList<>();
    public List<Integer> inorderTraversal(TreeNode root) {
         if (root == null) {
            return l;
        }
        inorderTraversal(root.left);
        l.add(root.val);
        inorderTraversal(root.right);
        return l;
    }
}