Easy data structure and algorithm practice puzzle.
Given an array and a value, remove every copy of that value and return what's left, in order. Use two pointers. The read pointer looks at every item. The write pointer only moves when you keep one: copy the item to the write spot and step it forward. Everything before the write pointer is your answer.
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 Read Throttle, a pipeline you can run and download. See every Software Engineer project.
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