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.
K Closest Elements
Implement a function to return the k closest elements to a target in a sorted array.
Level Order Traversal
Implement a function that performs a level order traversal of a binary tree and returns node values as a list of lists.
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.
Maximal rectangle in matrix
Given a matrix of 0s and 1s, compute the area of the largest rectangle consisting only of 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.
Validate BST
Implement a function to determine if a binary tree is a valid Binary Search Tree.
Kth Smallest in BST
Implement a function that returns the k-th smallest value in a binary search tree.
Count Complete Tree Nodes
Given a complete binary tree, return its node count faster than O(n) time.
Zigzag Level Order Traversal
Implement a function that returns the zigzag level-order traversal of a binary tree.
Maximum Width of a Binary Tree
Given the root of a binary tree, compute its maximum width (the maximum number of nodes in any level, counting null positions).
Rat in a Maze
Count the number of distinct paths a rat can take from top-left to bottom-right in a binary grid, moving down or right and avoiding walls.
Painter Partition Problem
Given board lengths and k painters, find the minimum possible maximum total length a painter must paint.
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.
Showing 1–24 of 47 challenges · medium
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.
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- 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.