Python coding challenges: "merge-sort"

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Lists & Arrays medium

Count Smaller Numbers

Given an integer list, return for each position how many later elements are smaller than it.

arrays counting merge-sort

+20 pts 20m

Data Structures & Algorithms hard

Count of Range Sum

Count contiguous subarrays whose sum lies in a given inclusive range using an efficient divide-and-conquer algorithm.

prefix-sum merge-sort divide-conquer

+35 pts 40m

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Guide: free Python coding challenges

Practice Python by solving problems

PythonSkillset challenges are hands-on coding exercises from beginner to advanced. Open a challenge, read the problem, write Python in the split-pane editor, and run tests with Pyodide — no install required.

How to use the arena

Pick a category — basics, algorithms, strings, and more
Open a challenge, read the statement, and edit the starter code
Run tests, fix failures, then try a related quiz or tutorial lesson

Challenges vs tutorials and quizzes

Challenges test what you can build under constraints. For guided teaching, use our Python tutorials. For quick checks, try quizzes or copy snippets from code samples.

Python Coding Challenges