Flood Fill Algorithm
Implement flood fill on a 2D grid using BFS/DFS.
2D Vector dataclass
Implement a Vector2D dataclass with +, -, scalar *, dot product, and magnitude.
Unique Paths with Obstacles
Given a 2D grid with obstacles, count the unique paths from top-left to bottom-right moving only down or right.
Maximal square
Given a 2D binary matrix of 0s and 1s, compute the area of the largest square containing only 1s.
Maximal square matrix
Given a 2D binary matrix of 0s and 1s, find the side length of the largest square containing only 1s.
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.
A* Pathfinding Heuristic
Implement A* search on a 2D grid to find the shortest path length between two cells.
Word Search Backtrack
Determine if a given word exists in a 2D board by tracing adjacent cells without reusing any cell.
Search 2D Matrix
Given a sorted 2D matrix with sorted rows and first element of each row greater than last of previous, find target efficiently.
Spiral Matrix Order
Given a 2D matrix, return all elements in clockwise spiral order starting from the top-left.
Number of Islands
Given a 2D grid of '1' (land) and '0' (water), count the number of islands surrounded by water.
Max Area of Island
Given a 2D grid of 0s and 1s, find the maximum area of a connected group of 1s.
Spiral Matrix Traversal
Implement a function that returns the elements of a 2D matrix in clockwise spiral order.
Search a 2D Matrix II
Implement an efficient search for a target in a matrix where each row and each column is sorted in ascending order.
Number of Islands in a Matrix
Count the number of distinct islands (connected groups of 1s) in a 2D binary matrix.
Shift 2D Grid
Implement a function to shift a 2D grid right by k positions, flattening the grid and wrapping elements.
Matrix Block Sum
Given a 2D matrix and a block size, compute the sum of each block centered at every cell.
Word Search Matrix
Given a 2D board and a word, determine if the word can be formed by sequentially adjacent cells (horizontally or vertically), without reusing cells.
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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.