Find Duplicate Number
Given a list of n+1 integers in the range 1..n, find the one integer that appears more than once.
Find Peak Element
Implement a function that returns the index of any peak element in an integer array.
K Closest Elements
Implement a function to return the k closest elements to a target in a sorted array.
Trie Insert and Search
Implement a Trie and a scenario runner that executes insert/search/prefix operations.
Design Skip List Lite
Implement a simplified skip list supporting insert, search, and delete with O(log n) average complexity.
Delete Node in BST
Implement a function that deletes a key from a binary search tree and returns the new root.
Validate BST
Implement a function to determine if a binary tree is a valid Binary Search Tree.
Kth Smallest in BST
Implement a function that returns the k-th smallest value in a binary search tree.
Zigzag Level Order Traversal
Implement a function that returns the zigzag level-order traversal of a binary tree.
Maximum Width of a Binary Tree
Given the root of a binary tree, compute its maximum width (the maximum number of nodes in any level, counting null positions).
A* Pathfinding Heuristic
Implement A* search on a 2D grid to find the shortest path length between two cells.
Word Search Backtrack
Determine if a given word exists in a 2D board by tracing adjacent cells without reusing any cell.
Painter Partition Problem
Given board lengths and k painters, find the minimum possible maximum total length a painter must paint.
Search in Rotated Array
Implement an efficient search in a rotated sorted array using modified binary search.
Interpolation Search
Implement interpolation search in Python on a sorted list of integers.
Ternary Search
Implement ternary search to locate the maximum of a discrete unimodal function.
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.
Koko Eating Bananas
Given piles of bananas and hours, find the minimum integer eating speed Koko needs to finish all piles within H hours.
Capacity to Ship Packages
Given package weights and days allowed, compute the smallest ship capacity that can deliver all packages in order within the given days.
Kth Missing Positive
Given a strictly increasing array and an integer k, return the k-th positive integer that is missing from the array.
Single Element in Sorted Array
Given a sorted array where every element appears exactly twice except one which appears once, return the single element.
Find in Mountain Array
Implement a function to search for a target value in a mountain array using binary search.
Maximum Running Time of n Computers
Use binary search to maximize the running time for n computers with batteries.
Magnetic Force Packages
Given basket positions and k balls, find the largest possible minimum distance between any two balls.
Showing 1–24 of 35 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.