Example: BST Inorder traversal - rFronteddu/general_wiki GitHub Wiki

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