Maximum subarray (Kadane)
Find the contiguous subarray with the largest sum.
Rotate array
Rotate a list right by k positions in place.
Remove duplicates (sorted)
Return a sorted list with duplicates removed.
Merge two sorted arrays
Merge two sorted arrays into one sorted array.
Product except self
Return an array where output[i] is the product of all elements except nums[i], without using division.
Sliding window maximum
Return the maximum of each window of size k as it slides across an array.
Second Largest Unique Value
Return the second largest distinct integer from a list, or None if it doesn't exist.
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.
Majority Element Finder
Implement a function that returns the majority element in a list, which appears more than half the time.
Find Duplicate Number
Given a list of n+1 integers in the range 1..n, find the one integer that appears more than once.
Partition Array
Implement a function that finds a contiguous partition of a list into k groups, minimizing the maximum sum of the groups.
Rearrange Positives and Negatives
Write a function that rearranges a list in-place so all negative numbers come before non-negative numbers.
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.
Pad Array Edges
Write a function that pads a list with zeros on both ends.
Count Smaller Numbers
Given an integer list, return for each position how many later elements are smaller than it.
Move Zeroes
Implement move_zeroes(nums) that in-place moves all zeros to the end while maintaining the order of non-zero elements.
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.
Running Total Window
Implement a function that returns a list of running totals, resetting to zero after each positive sum.
Normalize Array to Zero-One Range
Implement a function that normalizes a list of numbers to the range [0,1] using min-max scaling.
Showing 1–24 of 28 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.