Second Largest Unique Value
Return the second largest distinct integer from a list, or None if it doesn't exist.
Average excluding min and max
Return the average of a list after discarding the lowest and highest elements, handling edge cases.
Find Second Largest
Find the second largest unique number in a list, or None if it doesn't exist.
Move Zeros to End
Rearrange a list by moving all zeros to the end while preserving the relative order of non-zero elements.
Intersection of Two Lists
Given two lists, return a sorted list of unique elements that appear in both lists.
Wave sort array
Given a list of integers, reorder it into a wave pattern where elements alternate down-up, and return the new list.
Counting Sort
Implement the counting sort algorithm to sort a list of non-negative integers in O(n + k) time.
Count Smaller Numbers
Given an integer list, return for each position how many later elements are smaller than it.
Sort array by parity
Given a list of integers, return a new list with all evens first and odds last, preserving original relative order.
Merge Sorted Array In Place
Write a function that merges two sorted arrays into the first array in-place, keeping the result sorted.
Cartesian Product Pairs
Create a function that returns the Cartesian product of two lists as a sorted list of lists.
Sort List Merge Sort
Write a function that sorts a list of integers using the merge sort algorithm.
Insertion Sort
Implement insertion sort that sorts a list in-place and returns the same list.
Showing 1–13 of 13 challenges · Lists & Arrays
Lists & Arrays — Python coding challenges
What you will find here
This page lists lists & arrays 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.