First Bad Version
Implement a function to find the first bad version in a sorted range using binary search.
Find k Closest Elements to Target
Return exactly k elements from a sorted list that are closest to a given target, preserving order.
Two Sum Sorted
Given a 1-indexed sorted array and a target, return the two indices that add up to the target.
Squares of Sorted Array
Implement a function that returns a sorted list of squares for a given non-decreasing integer array.
Interval List Intersections
Given two lists of sorted, disjoint intervals, return the list of intersections between them.
Buildings with ocean view
Given building heights, return sorted indices of buildings that have a clear view of the ocean to their right.
Kth Largest Element in an Array (Heap Edition)
Implement a function that returns the kth largest element in an unsorted integer array using a heap.
Find K pairs with smallest sums
Given two sorted arrays and an integer k, return the k smallest pairs (u, v) with the smallest sums, sorted by sum.
Merge two sorted lists
Merge two ascending integer lists into one sorted list.
Search a 2D Matrix II
Implement an efficient search for a target in a matrix where each row and each column is sorted in ascending order.
Serialize dict to TOML-like
Convert nested Python dicts into a simplified TOML-like string with sorted keys, type-aware formatting, and flat table sections.
Customers Never Order
Given Customers and Orders tables, return the names of customers with no orders, sorted alphabetically, or None if all have ordered.
Showing 49–60 of 60 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.