Sliding Window Median
Given a list of integers and a positive window size k, return the median of each sliding window of length k.
Longest Repeating Character Replacement
Given a string and an integer k, return the length of the longest substring that can be made of identical characters after at most k replacements.
Remove K Digits Stack
Remove k digits from a non-negative integer string to produce the smallest possible number using a stack-based approach.
Validate Stack Sequences
Given two sequences of distinct integers, verify whether the second sequence is a valid pop order for a stack given the first sequence as push order.
Sum of Subarray Minimums
Given an integer array, sum the minimum of all contiguous subarrays modulo 10^9+7.
Top K Frequent Elements
Given an integer array and a number k, return the k most frequent elements using a heap-based approach.
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.
Top K Frequent Elements
Given a list of integers and a number k, return the k most frequent elements in descending order of frequency, with ties broken by larger value.
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.
Sliding Window Maximum using Heap
Given an array of integers and a window size k, return an array of maximums for each contiguous subarray of length k.
Merge two sorted lists
Merge two ascending integer lists into one sorted list.
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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.