Truncate with an ellipsis in Rust
Rust interview exercise on Strings, difficulty 1 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 truncate(s, max) that returns s unchanged if it has at most max characters, otherwise the first max characters followed by "…". Count characters, not bytes: slicing &s[..max] panics in the middle of a multi-byte character.
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.