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.
Euclidean Distance Matrix
Write a function to compute the Euclidean distance between every pair of points from two lists.
Generate a Multiplication Table
Build a function that returns an n x n multiplication table as a list of lists.
Concatenate Horizontally
Write a function that horizontally concatenates two 2D lists into a new 2D list.
Matrix addition operator
Implement a Matrix class that supports + and * operators.
Shortest Path in Binary Matrix
Implement BFS to find the shortest path length from (0,0) to (n-1,n-1) in an n x n binary matrix, moving through 0 cells in 8 directions.
Flood Fill Algorithm
Implement flood fill on a 2D grid using BFS/DFS.
Largest Area Histogram Matrix
Given a binary matrix, compute the largest rectangle area consisting entirely of 1s.
Maximal square
Given a 2D binary matrix of 0s and 1s, compute the area of the largest square containing only 1s.
Paint House Colors
Given a cost matrix, compute the minimum total cost to paint all houses with no two adjacent houses having the same color.
Maximal square matrix
Given a 2D binary matrix of 0s and 1s, find the side length of the largest square containing only 1s.
Minimum Falling Path Sum
Compute the minimum falling path sum in an n x n matrix by moving down or diagonally each step.
Matrix Chain Multiplication
Given a list of matrix dimensions, compute the minimum multiplication cost using dynamic programming.
Maximal rectangle in matrix
Given a matrix of 0s and 1s, compute the area of the largest rectangle consisting only of 1s.
Minimum Path Sum Matrix
Implement a function that computes the minimum path sum from the top-left to the bottom-right of a grid moving only right or down.
Dungeon Game Minimum Health
Compute the minimum initial health needed to reach the bottom-right corner of a dungeon grid without health dropping to zero or below.
Clique Detection
Given an undirected graph and a list of vertices, check if every pair of distinct vertices in the list is connected by an edge.
Surrounded Regions
Given an M×N grid of 'X' and 'O', capture all regions of 'O' that are completely surrounded by 'X'.
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.
Word Search Backtrack
Determine if a given word exists in a 2D board by tracing adjacent cells without reusing any cell.
Kth Smallest in Sorted Matrix
Implement kth_smallest(matrix, k) to return the kth smallest element in a row- and column-sorted square matrix.
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.
Showing 1–24 of 52 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.