Insert New Row
Implement a function that inserts a new row into a 2D list at a specified index.
Broadcast Add Scalar
Add a scalar to every number in a 2D list and return a new 2D list without modifying the original.
Fancy Index Select
Given a 2D matrix and a list of row indices, select those rows in order and return them as a new 2D list.
Reshape array dimensions
Implement a function that reshapes a 1D list into a 2D list with given dimensions.
Concatenate Horizontally
Write a function that horizontally concatenates two 2D lists into a new 2D list.
Dataclass with slots
Implement a slotted frozen dataclass representing a 2D point with total ordering.
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.
Cherry Pickup Maximum
Given a grid with cherries, find the maximum cherries you can collect using two paths from top-left to bottom-right.
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.
Toeplitz Matrix Check
Write a function is_toeplitz(matrix) that checks if a 2D list is a Toeplitz matrix, where all elements on the same diagonal from top-left to bottom-right are identical.
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.
Transpose Matrix In-Place
Implement a function that transposes a square matrix in-place and returns the transposed matrix.
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.
Matrix Multiply 2D
Write a function that multiplies two 2D matrices (lists of lists) and returns the product matrix.
Transpose 2D Array
Implement a function that returns the transpose of a rectangular 2D list.
Showing 29 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.