Practice Arena

Python Coding
Challenges

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925 challenges 556 easy 323 medium 46 hard

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All Python Basics Strings & Text Lists & Arrays Dicts & Sets Functions & Closures OOP & Classes Data Structures & Algorithms Advanced Python Iterators & Generators Decorators & Context Managers Error Handling & Exceptions Regular Expressions Math & Number Theory Bit Manipulation Dynamic Programming Trees & Binary Trees Graphs & Graph Algorithms Recursion & Backtracking Greedy Algorithms Binary Search Two Pointers & Sliding Window Stacks & Queues Heaps & Priority Queues Linked Lists Matrix & 2D Arrays Datetime & Time Calculations Data Formats & Parsing SQL & SQLite Numpy & Vectorized Computing Cryptography & Hashing

Greedy Algorithms medium

Queue Reconstruction by Height

Given shuffled pairs of (height, number_of_taller_people_in_front), reconstruct the original queue order.

greedy sorting insertion

Greedy Algorithms medium

Non-overlapping Intervals

Given a list of intervals, return the minimum number of intervals to remove to make the rest non-overlapping.

greedy intervals sorting

Greedy Algorithms medium

Max events attended

Given a list of events with start and end times, find the maximum number of non-overlapping events you can attend.

greedy interval-scheduling sorting

Binary Search medium

Find k Closest Elements to Target

Return exactly k elements from a sorted list that are closest to a given target, preserving order.

binary-search sorting two-pointers

Two Pointers & Sliding Window medium

Sort Colors (Dutch National Flag)

Implement the Dutch National Flag algorithm to sort an array of 0, 1, 2 in one pass.

in-place two-pointers sorting

Two Pointers & Sliding Window medium

Reverse Pairs Count

Implement a function to count reverse pairs in an array efficiently.

arrays counting sorting

Two Pointers & Sliding Window medium

Three Sum

Given an array of integers, return all unique triplets that sum to zero.

sorting two-pointer unique-triplets

Two Pointers & Sliding Window medium

Closest Three Sum

Given an array of integers and a target, return the sum of three numbers that is closest to the target.

sorting two-pointers array

Two Pointers & Sliding Window medium

Boats to Save People – Two Pointer

Implement a function that returns the minimum number of boats needed to rescue everyone, given a weight limit and each boat carrying at most two people.

two-pointers sorting greedy

Two Pointers & Sliding Window medium

Sliding Window Median

Given a list of integers and a positive window size k, return the median of each sliding window of length k.

sliding-window median sorting

Two Pointers & Sliding Window medium

Four Sum

Find all unique quadruplets in an array that sum to a given target.

two-pointers sorting set

Showing 25–35 of 35 challenges · medium

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.