Below are some challenge problems for CS 61A. Be forewarned that some of them are indeed, quite challenging. Because I am not involved in actually writing the exams, I can make no guarantees as to how similar the difficulty of these problems will be. However, in my past experience, these problems should be near exam-level or higher. The particularly difficult ones are marked as *Challenge*.
Mutable Data and Solutions
Object Oriented Programming and Solutions
Recursive Structures and Orders of Growth and Solutions
Midpoint Review and Solutions
Basic Scheme and Solutions
Advanced Scheme and Solutions
Iterators, Iterables, and Generators (and Streams) and Solutions