Pascal Triangle Row
Given a non-negative integer n, return the nth row of Pascal's triangle as a list of integers.
Catalan number
Implement a function that returns the nth Catalan number using dynamic programming.
Stirling number
Implement a function to compute Stirling numbers of the second kind S(n,k).
Stars and Bars Count
Implement stars_and_bars_count(n, k) which returns the number of ways to put n identical items into k distinct bins, with bins allowed to be empty.
Multinomial coefficient
Write a function to compute the multinomial coefficient efficiently for given nonnegative counts.
Binomial Coefficient
Implement a function to compute binomial coefficients modulo 10^9+7 for n up to 10^5.
Bell number
Implement a function to compute the Bell number B(n) using dynamic programming.
Unique Paths in a Grid
Count the number of unique paths from the top-left corner to the bottom-right corner of a grid, moving only right and down.
Target Sum Subsets
Write a function that counts the number of subsets of a list of positive integers that sum exactly to a target.
Unique Paths in a Grid
Count distinct paths in an m x n grid moving only down or right.
Derangement count
Implement a function to count derangements of n items using the classic recurrence.
Target sum assignments
Given a list of integers and a target, count how many ways to assign + or - to each number so the total equals the target.
Showing 1–12 of 12 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.