Two Sum
Return indices (i, j) with i < j such that nums[i] + nums[j] == target.
Maximum subarray (Kadane)
Find the contiguous subarray with the largest sum.
Rotate array
Rotate a list right by k positions in place.
Flatten nested list
Yield every integer from an arbitrarily nested list, depth-first.
Remove duplicates (sorted)
Return a sorted list with duplicates removed.
Merge two sorted arrays
Merge two sorted arrays into one sorted array.
Merge intervals
Merge all overlapping intervals and return a sorted result.
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.
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.
Second Largest Unique Value
Return the second largest distinct integer from a list, or None if it doesn't exist.
Move Zeros to the End
Reorder a list in-place, pushing all zeros to the end while preserving the order of non-zero numbers.
Chunk a list into n-sized parts
Write a function that divides a list into sublists of at most n elements.
Rotate Left by k
Implement a function that rotates a list left by k positions.
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.
Interleave Two Lists
Write a function that interleaves two lists element by element, preserving order.
Keep only even indexes
Given a list, return a new list containing only the elements at even indices (0, 2, 4, ...).
Running Maximum
Implement a function that returns a list where each element is the largest value seen so far.
Difference of Consecutive Elements
Given a list of numbers, return a new list where each element is the difference between consecutive elements.
All Unique Values Keep Order
Remove duplicates from a list, keeping only the first occurrence of each value while preserving relative order.
Partition around a pivot value
Implement an in-place partition of a list around a given pivot value, returning the boundary index.
Insert into a Sorted List
Implement a function that inserts a value into a sorted list at the correct position using binary search.
Average excluding min and max
Return the average of a list after discarding the lowest and highest elements, handling edge cases.
Showing 1–24 of 71 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.