Medium data structure and algorithm practice puzzle.
Given a sorted array a with empty space at the end, the number of real values m, and a second sorted array b, merge b into a and return it. Fill from the BACK. Compare the last real value in each and write the bigger one into the last open spot. Writing from the front would overwrite values you haven't read yet.
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 Reconciler, a pipeline you can run and download. See every Software Engineer project.
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