Largest Plus Sign
Compute the largest possible plus sign of 1s in an n x n grid with some cells set to 0.
Matrix Block Sum
Given a 2D matrix and a block size, compute the sum of each block centered at every cell.
Rotate Matrix Layers
Given a square matrix, rotate each concentric layer 90 degrees clockwise.
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.
Pacific Atlantic Flow
Given a height matrix, return all cells from which water can flow to both the Pacific and Atlantic oceans.
Pacific Atlantic Matrix DFS
Given a matrix of heights, return cells that can reach both Pacific and Atlantic oceans using a DFS approach.
Flatten matrix to vector
Read rows left-to-right, top-to-bottom.
Transpose a matrix
Swap rows and columns for a rectangular matrix.
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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.