Trim BST to range
Implement a function to trim a BST to only retain nodes with values in a given inclusive range.
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.
Zigzag Level Order Traversal
Implement a function that returns the zigzag level-order traversal of a binary tree.
Cycle Detection in Undirected Graph
Write a function that detects if an undirected graph contains a cycle.
Articulation Points
Implement a function that returns the articulation points of an undirected graph.
Bridges in Graph
Implement a function that returns all bridges in an undirected graph.
Hamiltonian Path Check
Implement a function that checks whether an undirected graph has a Hamiltonian path using DFS and backtracking.
Bipartite Graph Check
Implement a function to check if an undirected graph is bipartite using graph coloring.
Cheapest Flights Within K Stops
Implement a function to compute the cheapest flight price from source to destination with at most K stops in a directed weighted graph.
Find center of star graph
Write a function that finds the center node of a star graph from its list of edges in O(1) time.
Strongly Connected Components (Kosaraju's Algorithm)
Implement a function to find strongly connected components in a directed graph using Kosaraju's algorithm.
Minimum Genetic Mutation
Implement a function to compute the minimum number of single-character mutations needed to transform one gene string into another, using a given bank of valid mutations.
Jump Game on Graph
Implement a function that determines if you can reach the last node of a directed graph by jumping from node 0 to node n-1 using edges.
Wildcard Match (Simple)
Write a function that checks whether a string matches a pattern with '*' and '?' wildcards.
Permutation Generator
Write a function that returns all permutations of a list of distinct integers.
Combination Generator
Write a recursive function that returns all combinations of length k from a list of distinct integers.
Permutations
Write a function that returns every permutation of the elements in the input list.
Partition Equal Subset Sum (Backtracking)
Write a function that uses backtracking to decide if a list of positive integers can be partitioned into two subsets with equal sum.
Power set from set
Write a function to return the power set of a given list of distinct elements.
Ternary Search
Implement ternary search to locate the maximum of a discrete unimodal function.
Find Minimum in Rotated Sorted Array
Implement a function that finds the minimum element in a rotated sorted array of distinct integers in O(log n) time.
Find in Mountain Array
Implement a function to search for a target value in a mountain array using binary search.
Binary Search on Answer: Find the Minimal Maximum Subarray Sum
Implement a function that finds the minimal possible maximum subarray sum when splitting an array into at most k contiguous subarrays.
Showing 289–312 of 365 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.