94. Binary Tree Inorder Traversal

class Solution {
    public List<Integer> inorderTraversal(TreeNode root) {
        List<Integer> result = new ArrayList<Integer>();
        helper(root, result);
        return result;
    }
    
    private void helper(TreeNode root, List<Integer> result) {
        if (root != null) {
            if (root.left != null) {
                helper(root.left, result);
            }
            result.add(root.val);
            
            if (root.right != null) {
                helper(root.right, result);
                
            }
        }
    }
}

Inorder, Postorder, Preorder 공부하기!
코드로 어떻게 짜는지! 공부하기!

Runtime: 0 ms, faster than 100.00% of Java online submissions for Binary Tree Inorder Traversal.
Memory Usage: 37.1 MB, less than 78.14% of Java online submissions for Binary Tree Inorder Traversal.