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Python Coding
Challenges

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925 challenges 556 easy 323 medium 46 hard

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All Python Basics Strings & Text Lists & Arrays Dicts & Sets Functions & Closures OOP & Classes Data Structures & Algorithms Advanced Python Iterators & Generators Decorators & Context Managers Error Handling & Exceptions Regular Expressions Math & Number Theory Bit Manipulation Dynamic Programming Trees & Binary Trees Graphs & Graph Algorithms Recursion & Backtracking Greedy Algorithms Binary Search Two Pointers & Sliding Window Stacks & Queues Heaps & Priority Queues Linked Lists Matrix & 2D Arrays Datetime & Time Calculations Data Formats & Parsing SQL & SQLite Numpy & Vectorized Computing Cryptography & Hashing

Trees & Binary Trees medium

Kth Smallest in BST

Implement a function that returns the k-th smallest value in a binary search tree.

bst inorder recursion

Trees & Binary Trees easy

Range Sum BST

Return the sum of all node values in a BST that lie within a given inclusive range [low, high].

bst tree recursion

Trees & Binary Trees medium

Count Complete Tree Nodes

Given a complete binary tree, return its node count faster than O(n) time.

binary-tree complete-tree tree-traversal

Trees & Binary Trees medium

Zigzag Level Order Traversal

Implement a function that returns the zigzag level-order traversal of a binary tree.

binary-tree breadth-first-search queue

Trees & Binary Trees medium

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).

binary-tree breadth-first-search queue

Graphs & Graph Algorithms medium

Graph Valid Tree

Determine if n nodes and an edge list form a valid tree (connected and acyclic).

Graphs & Graph Algorithms medium

Prim's Minimum Spanning Tree

Given a connected undirected weighted graph, compute the total weight of its minimum spanning tree using Prim's algorithm.

graphs mst prim

Graphs & Graph Algorithms medium

Kruskal MST

Implement Kruskal's algorithm to compute the total weight of a minimum spanning tree in a connected undirected graph.

graphs minimum-spanning-tree union-find

Graphs & Graph Algorithms medium

Minimum Height Trees

Given an undirected tree, find all root nodes that minimize the height of the tree.

graphs bfs topological

Showing 25–33 of 33 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.