Count subsets with sum
Given a list of integers and a target sum, count how many subsets of the list sum to the target.
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.
Subset Sum Exists
Given a list of positive integers and a target sum, return whether some subset adds up exactly to the target.
Delete and Earn
Given an array of integers, find the maximum points you can earn by repeatedly deleting a number and all its adjacent values.
Combination Generator
Write a recursive function that returns all combinations of length k from a list of distinct integers.
Permutations II
Return all distinct permutations of a list of integers that may include duplicates.
Subsets
Return all subsets (the power set) of a list of distinct integers.
Subsets II
Given a collection of integers that might contain duplicates, return all possible unique subsets.
Partition Equal Subset Sum (Backtracking)
Write a function that uses backtracking to decide if a list of positive integers can be partitioned into two subsets with equal sum.
Combination Sum
Given a list of distinct positive integers and a target, return all unique combinations that sum to the target.
Jump Game Reachable
Given an array of non-negative integers where each element is the maximum jump length, determine if you can reach the last index.
Interpolation Search
Implement interpolation search in Python on a sorted list of integers.
Find Minimum in Rotated Sorted Array
Implement a function that finds the minimum element in a rotated sorted array of distinct integers in O(log n) time.
Koko Eating Bananas
Given piles of bananas and hours, find the minimum integer eating speed Koko needs to finish all piles within H hours.
Kth Missing Positive
Given a strictly increasing array and an integer k, return the k-th positive integer that is missing from the array.
Minimum Speed to Arrive on Time
Given commute distances and a time limit, compute the minimum integer speed so you arrive on time.
Nth Magical Number
Given three integers n, a, b, return the nth positive integer that is divisible by either a or b.
Count Nice Subarrays
Given an array of integers, count the number of contiguous subarrays that contain exactly k odd numbers.
Three Sum
Given an array of integers, return all unique triplets that sum to zero.
Closest Three Sum
Given an array of integers and a target, return the sum of three numbers that is closest to the target.
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.
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.
Trapping Rain Water (Two Pointers)
Given an array of non-negative integers representing elevation heights, compute how much water can be trapped after rain.
Showing 25–48 of 59 challenges · medium
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.