It filters the first <list> by membership in the second <list>, retaining the order and all repetitions of qualifying entries in the first <list>. For example, `mystery3([3, 1, 3, 2], [3, 4])` returns \b[`[3, 3]`]. Thus it is related to <set intersection>, but its result is a <list> and does not discard repeated elements.

Solution

Past exam of the mathematical and Computational Biology course of the University of Cambridge / 2025 / Paper 1 / 1 / c / Solution

 Solution (source code)