Run-length encoding in Java
Java interview exercise on Strings, 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 compress(s) that replaces every run of the same character by the character followed by the run's length, leaving out the length when it is 1.
Walk the string once with an index that jumps to the end of each run.
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.