Fibonacci(n)
Return the nth Fibonacci number efficiently.
Maximum subarray (Kadane)
Find the contiguous subarray with the largest sum.
Coin change (DP)
Find the minimum number of coins to make exactly the target amount.
Longest increasing subsequence
Return the length of the longest strictly increasing subsequence.
Levenshtein Distance
Implement the classic Levenshtein distance algorithm to measure string similarity.
Kadane Variant: Maximum Product Subarray
Implement max_product_subarray(nums) that returns the maximum product of any contiguous subarray.
Bell number
Implement a function to compute the Bell number B(n) using dynamic programming.
Climbing Stairs
Implement a function that returns the number of distinct ways to climb n stairs using steps of 1 or 2.
Longest Palindromic Subsequence
Compute the length of the longest palindromic subsequence in a given string.
0/1 Knapsack
Implement the classic 0/1 Knapsack dynamic programming solution to maximize value under a weight capacity.
Target Sum Subsets
Write a function that counts the number of subsets of a list of positive integers that sum exactly to a target.
Coin Change Minimum
Given coin denominations and a target amount, compute the minimum number of coins needed or -1 if impossible.
Perfect Squares Sum
Given a positive integer n, return the least number of perfect squares (e.g., 1, 4, 9, 16, ...) that sum to n.
Word Break DP
Implement a function to check if a string can be segmented into space-separated dictionary words.
Buy Sell Stock with Cooldown (DP)
Given daily stock prices, compute the maximum profit you can achieve if you must wait one day after selling before buying again.
Longest Arithmetic Subsequence
Given a list of integers, return the length of the longest arithmetic subsequence (constant difference) within it.
Shortest Common Supersequence
Given two strings, return any shortest supersequence that contains both as subsequences.
Interleaving string
Given three strings s1, s2, and s3, check if s3 is formed by interleaving s1 and s2 while preserving the order of each input string.
Matrix Chain Multiplication
Given a list of matrix dimensions, compute the minimum multiplication cost using dynamic programming.
Subset Sum Exists
Given a list of positive integers and a target sum, return whether some subset adds up exactly to the target.
Cheapest Flights Within K Stops
Implement a function to compute the cheapest flight price from source to destination with at most K stops in a directed weighted graph.
Business days between
Calculate the number of business days (Mon-Fri) between two dates, inclusive of both endpoints.
Showing 1–22 of 22 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.