Substring Anagrams
Return all start indices in a string where a substring of length k is an anagram of a pattern string.
Hash map merge
Write a function that merges two dictionaries recursively, combining values and preserving structure.
Class Method Factory
Create a class method factory that dynamically adds methods to a class based on a mapping of names to behaviors.
Decode Ways
Count the number of ways to decode a numeric string into letters using the mapping A=1 to Z=26.
Longest Arithmetic Subsequence
Given a list of integers, return the length of the longest arithmetic subsequence (constant difference) within it.
Delete and Earn
Given an array of integers, find the maximum points you can earn by repeatedly deleting a number and all its adjacent values.
Letter Combinations of a Phone Number
Given a string of digits, return all possible letter combinations that the number could represent on a phone keypad.
Partition Labels
Partition a string into maximal parts where each character appears in only one part, returning part lengths.
Character Replacement Window
Given a string and a number k, find the length of the longest substring that can be made uniform by replacing at most k characters.
Permutation in String
Determine if any permutation of a shorter string appears as a contiguous substring in a longer string using an efficient sliding window.
Fruit into Baskets
Given an array of integers representing fruit types, return the maximum number of fruits you can collect in a contiguous subarray with at most two distinct types.
Longest Substring with At Most K Distinct Characters
Given a string and an integer k, find the length of the longest substring that contains at most k distinct characters.
Longest Repeating Character Replacement
Given a string and an integer k, return the length of the longest substring that can be made of identical characters after at most k replacements.
Top K Frequent Elements
Given an integer array and a number k, return the k most frequent elements using a heap-based approach.
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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.