Longest Substring with K Repeating Characters
Return the length of the longest substring of a given string in which every character appears at least K times.
Jump Game Minimum Jumps
Given an array of non-negative integers where each element is the maximum jump length, compute the minimum jumps to reach the last index.
Find all anagrams
Return all starting indices where any anagram of a given word appears as a substring.
Substring Anagrams
Return all start indices in a string where a substring of length k is an anagram of a pattern string.
Sliding window maximum
Return the maximum of each window of size k as it slides across an array.
Running Total Window
Implement a function that returns a list of running totals, resetting to zero after each positive sum.
Rolling Window Mean
Given a list of numbers and a window size k, return a list of the means of every contiguous subarray of length k.
Convolve 1D Signal
Write a function that computes the 1D convolution of two lists in 'full' mode.
Consecutive available seats
Given a list of seat statuses, return the length of the longest consecutive run of available (0) seats.
Window Iterator
Implement a generator that yields consecutive windows of a given size from any iterable.
Best Time to Buy and Sell Stock
Given a list of daily stock prices, determine the maximum profit achievable by buying on one day and selling on a later day.
Longest Substring Without Repeating Characters
Implement a function that returns the length of the longest substring without repeating characters.
Minimum Window Substring
Implement a sliding window algorithm to find the minimum window substring containing all characters of a given pattern.
Character Replacement Window
Given a string and a number k, find the length of the longest substring that can be made uniform by replacing at most k characters.
Permutation in String
Determine if any permutation of a shorter string appears as a contiguous substring in a longer string using an efficient sliding window.
Count Nice Subarrays
Given an array of integers, count the number of contiguous subarrays that contain exactly k odd numbers.
Subarrays with K different ints
Count the number of contiguous subarrays that contain exactly K distinct integers.
Minimum Size Subarray Sum
Given an array of positive integers, return the minimal length of a contiguous subarray with sum at least target, or 0 if none exists.
Fruit into Baskets
Given an array of integers representing fruit types, return the maximum number of fruits you can collect in a contiguous subarray with at most two distinct types.
Binary Subarray with Sum
Given a binary list and a goal sum, count the number of subarrays that add up to that goal.
Subarray product less than K
Count contiguous subarrays where the product of all elements is strictly less than a target K.
Longest Substring with At Most K Distinct Characters
Given a string and an integer k, find the length of the longest substring that contains at most k distinct characters.
Minimum Window Subsequence
Given strings s and t, return the minimum window substring of s that contains t as a subsequence, or empty string if none exists.
Sliding Window Median
Given a list of integers and a positive window size k, return the median of each sliding window of length k.
Showing 1–24 of 27 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.