Lifetimes: the longer of two in Rust
Rust interview exercise on Ownership & Borrowing, difficulty 2 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 longest(a, b) that returns whichever string slice has more characters; a wins a tie. The result could borrow from either argument, so the signature needs a lifetime that covers both.
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.