BFS level-order traversal
Return the level-order traversal of a binary tree as a list of lists.
Find Peak Element
Implement a function that returns the index of any peak element in an integer array.
Path Sum II All Paths
Return all root-to-leaf paths where the sum of node values equals a target.
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.
Maximal square
Given a 2D binary matrix of 0s and 1s, compute the area of the largest square containing only 1s.
Lowest Common Ancestor in a Binary Tree
Implement a function to find the lowest common ancestor (LCA) of two nodes in a binary tree.
Sum Root to Leaf Numbers
Given the root of a binary tree, compute the total sum of all root-to-leaf numbers.
Binary tree left side view
Given a binary tree, return the leftmost node's value at each depth, from top to bottom.
Vertical Order Traversal
Compute the vertical order traversal of a binary tree, grouping nodes by column and row.
Delete Node in BST
Implement a function that deletes a key from a binary search tree and returns the new root.
Search in Rotated Array
Implement an efficient search in a rotated sorted array using modified binary search.
Interpolation Search
Implement interpolation search in Python on a sorted list of integers.
Ternary Search
Implement ternary search to locate the maximum of a discrete unimodal function.
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.
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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.