Easy data structure and algorithm practice puzzle.
Given an array and a target, return the index of the first match, or -1 if it isn't there. Check each item from the front. It's O(n), but it works on any array. Binary search is faster, but only because it gets to demand sorted input.
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 Ledger Balancer, a pipeline you can run and download. See every Software Engineer project.
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