Open the Lock BFS
Implement a BFS solution to find the minimum number of turns needed to open a 4-wheel lock, avoiding a set of deadends.
Minimum Genetic Mutation
Implement a function to compute the minimum number of single-character mutations needed to transform one gene string into another, using a given bank of valid mutations.
Possible bipartition
Given N people and a list of mutual dislikes, check if they can be divided into two groups with no dislike inside a group.
Graph Coloring Backtrack
Given an adjacency list and a number of colors, decide if the graph can be colored so no adjacent vertices share a color.
Android unlock patterns
Count the number of valid Android unlock patterns of a given length using a 3x3 grid with adjacency constraints.
Floyd-Warshall: All-Pairs Shortest Paths
Implement the Floyd-Warshall algorithm to find all-pairs shortest path distances in a directed graph with possibly negative weights but no negative cycles.
Jump Game on Graph
Implement a function that determines if you can reach the last node of a directed graph by jumping from node 0 to node n-1 using edges.
Most stones removed
Given stone coordinates on a grid, find the maximum number of stones that can be removed while every stone shares a row or column with another remaining stone.
Number of Islands
Given a 2D grid of '1' (land) and '0' (water), count the number of islands surrounded by water.
Pacific Atlantic Flow
Given a height matrix, return all cells from which water can flow to both the Pacific and Atlantic oceans.
Showing 25–34 of 34 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.