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.
Count nodes in a linked list
Return how many values appear in the list (one per node).
Read the head node value
Return the first value or None when the list is empty.
Read the tail node value
Return the last value or None when the list is empty.
Reverse a linked list copy
Return a new list with node values in reverse order without mutating the input.
Concatenate two linked lists
Append the second list's nodes after the first and return a new list.
Value at index n
Return the value at zero-based index n or None if out of range.
Middle node index
Return the floor middle index for a non-empty list.
Sum all node values
Add every integer payload in the list.
Maximum node value
Return the largest integer or None when empty.
Remove the head node
Return a new list without the first node.
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.
Showing 1–24 of 29 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.