Longest Substring with K Repeating Characters
Return the length of the longest substring of a given string in which every character appears at least K times.
Design Twitter Feed
Implement a Twitter class with postTweet, getNewsFeed, follow, and unfollow methods.
Longest Consecutive Sequence
Given an unsorted list of integers, find the length of the longest consecutive elements sequence in O(n) time.
Merge time intervals
Given a list of time intervals, merge all overlapping intervals and return the merged intervals.
Delete Middle Node
Implement a function that deletes a given non-tail node from a singly linked list in O(1) time.
Context manager timer
Implement a Timer context manager that records elapsed seconds.
Retry decorator
Implement @retry(times=3) that retries a function on exception.
Memoize with TTL
Implement a decorator that caches function results for a limited time, returning cached values within the TTL and recomputing after expiry.
Rate Limit Decorator
Implement a decorator that enforces a maximum number of calls per second for any function.
Profile time decorator
Create a decorator that tracks how many times a function is called and its cumulative execution time.
Count Complete Tree Nodes
Given a complete binary tree, return its node count faster than O(n) time.
Network Delay Time
Given a directed weighted graph and a starting node, find the minimum time for a signal to reach all nodes, or -1 if unreachable.
Meeting Rooms Minimum
Given a list of meeting time intervals, compute the minimum number of conference rooms required.
Max events attended
Given a list of events with start and end times, find the maximum number of non-overlapping events you can attend.
Find Minimum in Rotated Sorted Array
Implement a function that finds the minimum element in a rotated sorted array of distinct integers in O(log n) time.
Maximum Running Time of n Computers
Use binary search to maximize the running time for n computers with batteries.
Minimum Speed to Arrive on Time
Given commute distances and a time limit, compute the minimum integer speed so you arrive on time.
Count nodes equal to target
Count how many times target appears in the list.
Rotting Oranges Time
Given a grid of fresh, rotten, and empty cells, compute the minimum minutes until all fresh oranges rot, or -1 if some are unreachable.
Julian Day Number Converter
Implement two functions to convert between Gregorian calendar dates and Julian Day Numbers using a standard formula.
Easter Date Calculator
Implement a function that returns the date of Easter Sunday for a given year using the Gregorian computus algorithm.
Showing 1–21 of 21 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.