Easy data structure and algorithm practice puzzle.
Given an array of 1s and 0s, return the length of the longest run of 1s in a row. Keep a counter that goes up on a 1 and resets to 0 on a 0, and update your best every time the counter grows. The common bug is only checking the best when a run ends, which misses a run that goes all the way to the end.
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 Login Range Service, a pipeline you can run and download. See every Software Engineer project.
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