AST Visitor Lite
Implement a depth-first traversal of a simplified AST and return identifier names in order.
Merge time intervals
Given a list of time intervals, merge all overlapping intervals and return the merged intervals.
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.
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.
Delete Middle Node
Implement a function that deletes a given non-tail node from a singly linked list in O(1) time.
Design Browser History
Implement a BrowserHistory class that supports visit, back, and forward navigation with step counts.
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.
Strobogrammatic number II
Given a positive integer n, return all strobogrammatic numbers of length n in ascending order.
Showing 25–36 of 36 challenges · medium · Data Structures & Algorithms
Data Structures & Algorithms — Python coding challenges
What you will find here
This page lists data structures & algorithms challenges — real Python problems you solve in the browser IDE with instant test feedback. Each challenge includes a clear brief, starter code, and automated checks.
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.