It’s usually just a problem and sometimes a simple example I can write as a test case for correctness. Some cards I’ve put in lately are: Calculate the level

It’s usually just a problem and sometimes a simple example I can write as a test case for correctness. Some cards I’ve put in lately are: Calculate the level of a binary tree with the minimal sum of its elements. Reconstruct a binary tree given an inorder and preorder list of the nodes. The backs are usually blank or space and time complexities that I should be able to achieve.