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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 medium

Count inversions lite

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

inversions sorting merge sort

Data Structures & Algorithms easy

Count pairs with given difference

Count how many unordered pairs in a list have a given absolute difference using an efficient approach.

hash map counting arrays

Data Structures & Algorithms medium

Radix Sort

Implement LSD radix sort to sort a list of non-negative integers in ascending order.

radix-sort sorting counting-sort

Data Structures & Algorithms medium

Decode Ways

Count the number of ways to decode a numeric string into letters using the mapping A=1 to Z=26.

dynamic programming strings counting

Data Structures & Algorithms hard

Count of Range Sum

Count contiguous subarrays whose sum lies in a given inclusive range using an efficient divide-and-conquer algorithm.

prefix-sum merge-sort divide-conquer

Data Structures & Algorithms easy

Consecutive available seats

Given a list of seat statuses, return the length of the longest consecutive run of available (0) seats.

arrays sliding-window greedy

Data Structures & Algorithms medium

Arithmetic Slices Count

Given a list of integers, count how many contiguous subarrays of length at least 3 form an arithmetic sequence.

arrays arithmetic counting

Data Structures & Algorithms hard

Knight Tour Count

Implement a backtracking search to count all ways a knight can visit every cell on a 5x5 board exactly once starting from (0,0).

backtracking dfs board

Showing 1–8 of 8 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.