Quick check

Five warm-ups, no hints

• One problem per core skill: walking an array, moving things in place, a missing number, words in a string, and counting.
• Aim for about 25 minutes. The clock is a guide; nothing stops when it runs out.
• Run the tests as often as you like. Stuck? Skip it: that's what the check is for.
• Pass 4 or more and you're ready for roadmap level 1. Anything you miss goes on your revise list, and the warm-ups pick up from the first one you missed.