Isomorphic Strings Check
Given two strings, check if they are isomorphic by verifying a one-to-one character mapping.
Substring Anagrams
Return all start indices in a string where a substring of length k is an anagram of a pattern string.
Two Sum with Dict
Implement the classic Two Sum problem: return indices of two numbers that add up to a target using a dict.
Count Pairs with Sum
Implement a function that counts the number of distinct pairs in a list summing to a target.
Longest Harmonious Subsequence
Given a list of integers, find the length of the longest harmonious subsequence where the difference between maximum and minimum values is exactly 1.
Employees earning more than manager
Given employee records with manager IDs, find those who earn more than their direct manager.
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.
Longest Substring Without Repeating Characters
Implement a function that returns the length of the longest substring without repeating characters.
Minimum Window Substring
Implement a sliding window algorithm to find the minimum window substring containing all characters of a given pattern.
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.
Showing 1–13 of 13 challenges
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.