Medium data structure and algorithm practice puzzle.
Given a list of words, return how many words start with the same letter as the word right before them, ignoring case. So she, sells, sea, shells is 3. Start at the second word and compare it with the one before. Looking back instead of forward keeps you from running off 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 Track Billing Run, a pipeline you can run and download. See every Software Engineer project.
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