Number of Islands
Given a 2D grid of '1' (land) and '0' (water), count the number of islands surrounded by water.
01 Matrix Nearest Zero
Given a binary matrix, return a matrix of the same shape where each cell contains the Manhattan distance to the nearest 0.
Rotting Oranges Time
Given a grid of fresh, rotten, and empty cells, compute the minimum minutes until all fresh oranges rot, or -1 if some are unreachable.
Number of Islands in a Matrix
Count the number of distinct islands (connected groups of 1s) in a 2D binary matrix.
Shortest Path in Binary Matrix
Compute the shortest path length from top-left to bottom-right in a binary matrix using 8-directional moves.
Pacific Atlantic Flow
Given a height matrix, return all cells from which water can flow to both the Pacific and Atlantic oceans.
Showing 25–30 of 30 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.