Reconstruct Itinerary
Given a list of airline tickets, reconstruct the itinerary in order using each ticket exactly once, choosing the lexicographically smallest path when multiple options exist.
Find Peak Index
Given a list of integers, return the index of any peak element where the value is not smaller than its neighbors.
Peak Element in Array
Implement a function that returns the index of any peak element in a list of integers.
Design Front Middle Back Queue
Implement a data structure that supports push/pop at front, middle, and back of a queue.
Merge Two Sorted Lists
Write a function that merges two sorted lists into a single sorted list.
Jump Search
Implement the jump search algorithm to locate a target in a sorted list, returning its index or -1.
Eulerian Path Check
Given the number of vertices and an edge list of an undirected graph, decide if it has an Eulerian path.
Merge time intervals
Given a list of time intervals, merge all overlapping intervals and return the merged intervals.
Delete Old Records
Filter a list of records by removing those with a date older than a given cutoff date.
Top N per group
Implement top_n_per_group that returns the top N scores for each group from a list of (group, score) pairs.
Consecutive available seats
Given a list of seat statuses, return the length of the longest consecutive run of available (0) seats.
Argsort Indices
Implement a function that returns the indices that would sort a list of integers, with ties broken by original order.
Level Order Traversal
Implement a function that performs a level order traversal of a binary tree and returns node values as a list of lists.
Matchsticks to Square
Given a list of matchstick lengths, decide if they can form a square by using each matchstick exactly once.
Merge K Sorted Lists
Write a function that merges multiple sorted lists into a single sorted list.
Memory view slice
Implement chunk_list that splits a list into consecutive sublists of a given chunk size.
Delete Middle Node
Implement a function that deletes a given non-tail node from a singly linked list in O(1) time.
Design Skip List Lite
Implement a simplified skip list supporting insert, search, and delete with O(log n) average complexity.
Delete duplicates sorted II
Given a sorted list, remove duplicates in place so each element appears at most twice, returning the new length.
Arithmetic Slices Count
Given a list of integers, count how many contiguous subarrays of length at least 3 form an arithmetic sequence.
Accounts Merge
Given a list of accounts, merge those that share any email and return sorted accounts.
Multiprocessing Queue
Implement a function that uses a multiprocessing queue to compute factorials of a list of numbers in parallel.
Custom iterator class
Implement a custom iterator class that repeatedly yields elements from a list up to a given number of times.
Generator Pipeline
Implement a generator function that yields only even numbers from an input list, squared.
Showing 145–168 of 273 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.