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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

Data Structures & Algorithms hard

LRU cache decorator

Implement @lru_cache(maxsize=N) for unary functions using OrderedDict.

decorators caching OrderedDict

Data Structures & Algorithms easy

Index of peak element

Implement a function that returns the index of any peak element in a given integer array.

arrays search peak

Data Structures & Algorithms medium

Count inversions lite

Implement a function that counts inversions in a list of numbers efficiently.

inversions sorting merge sort

Data Structures & Algorithms medium

Find Peak Element

Implement a function that returns the index of any peak element in an integer array.

arrays search binary-search

Data Structures & Algorithms easy

Peak Element in Array

Implement a function that returns the index of any peak element in a list of integers.

array search indices

Data Structures & Algorithms medium

K Closest Elements

Implement a function to return the k closest elements to a target in a sorted array.

arrays binary-search sorting

Data Structures & Algorithms easy

Merge Two Sorted Lists

Write a function that merges two sorted lists into a single sorted list.

merge sorting lists

Data Structures & Algorithms easy

Argsort Indices

Implement a function that returns the indices that would sort a list of integers, with ties broken by original order.

sorting indices lists

Data Structures & Algorithms medium

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.

binary-tree queue bfs

Data Structures & Algorithms easy

Lowest Common Ancestor in a Binary Search Tree

Implement a function to find the lowest common ancestor of two node values in a binary search tree.

Data Structures & Algorithms hard

N-Queens Solutions

Implement a function to count the number of distinct ways to place n queens on an n×n board.

backtracking chess recursion

Data Structures & Algorithms hard

Merge K Sorted Lists

Write a function that merges multiple sorted lists into a single sorted list.

merge sorting heap

Data Structures & Algorithms easy

Memory view slice

Implement chunk_list that splits a list into consecutive sublists of a given chunk size.

slicing lists chunking

Data Structures & Algorithms medium

Delete Middle Node

Implement a function that deletes a given non-tail node from a singly linked list in O(1) time.

linked-list pointer in-place

Showing 1–14 of 14 challenges · Data Structures & Algorithms

Data Structures & Algorithms — Python coding challenges

What you will find here

This page lists data structures & algorithms challenges — real Python problems you solve in the browser IDE with instant test feedback. Each challenge includes a clear brief, starter code, and automated checks.

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.