A generic, enumerable container in C#
C# interview exercise on Classes & Records, difficulty 3 of 3. Solve it in the editor beside a worked example, or cold in Interview mode with the example hidden; the tests run the moment you do.
Write SimpleStack<T> with Push, Pop and Peek (both throwing InvalidOperationException("stack is empty") when empty) and Count. Implement IEnumerable<T>, yielding from the top down, so foreach and LINQ work on it.
Each exercise pairs a worked example with a twin problem to solve in a real editor; the tests run the moment you do. Interview mode hides the example: solve it from memory, without the hint or the solution, and it counts as solved cold. Progress is saved in your browser, and in your account if you sign in.