Running Product of Integers
Given a list of integers, return a new list where each element at index i is the product of all elements from index 0 to i.
Find Missing Number 1 to n
Given a list containing n-1 distinct integers from 1 to n, find the missing number without using extra space.
Product of All Except Zeros Handling
Given a list of integers, return a list where each element is the product of all other elements, handling zeros correctly.
Find Duplicate Number
Given a list of n+1 integers in the range 1..n, find the one integer that appears more than once.
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.
Two Missing Numbers
Given a list of n-2 unique integers from 1 to n, find the two missing numbers efficiently.
Three Missing Numbers
Find the three missing numbers from a shuffled list containing all but three integers from 1 to n.
Sort array by parity
Given a list of integers, return a new list with all evens first and odds last, preserving original relative order.
Count Adjacent Pairs
Given a list of integers and a target, count adjacent pairs whose sum equals the target.
Sort List Merge Sort
Write a function that sorts a list of integers using the merge sort algorithm.
Flatten Multidimensional Lists
Write a function that flattens arbitrarily nested lists of integers into a single list.
Showing 1–12 of 12 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.