Easy data structure and algorithm practice puzzle.
Given the token count of each chat message, oldest first, and a token budget, return how many messages you can keep. Newest messages matter most, so start from the end and walk backwards, adding messages while they still fit. Stop at the first one that doesn't. That's how a chatbot trims history to fit its context window.
Solve it three ways: snap the jigsaw pieces together, fill in the blanks, or type it from scratch against the tests. This one is free.
Every line of the solution comes with a note explaining why it is there, and a step by step replay shows the code running. At level 3, where you type it yourself, you can ask for an AI mock interview on this problem that ends with a hiring manager's scorecard.
Then grow it into a real project with the Software Engineer button: this puzzle becomes the Request Coverage Report, a pipeline you can run and download. See every Software Engineer project.
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