Linked list reversal
Implement a singly linked list and a function to reverse it in place.
Design Front Middle Back Queue
Implement a data structure that supports push/pop at front, middle, and back of a queue.
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.
Prepend a new head
Insert value at the front of the list.
Append a new tail
Add value after the last node.
Palindrome linked values
Check whether values read the same forwards and backwards.
Rotate list left by k
Move the first k nodes to the end (k may exceed length; use modulo).
Merge two sorted lists
Merge two ascending integer lists into one sorted list.
Remove duplicate values
Keep first occurrence of each value while preserving order.
Pairwise sum of adjacent nodes
Sum each adjacent pair; keep a lone last node as-is.
Count nodes equal to target
Count how many times target appears in the list.
Zip two linked lists
Interleave values from a and b until both are exhausted.
Split list at index
Return prefix and suffix tuples at index k.
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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.