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.
Count Adjacent Pairs
Given a list of integers and a target, count adjacent pairs whose sum equals the target.
Cartesian Product Pairs
Create a function that returns the Cartesian product of two lists as a sorted list of lists.
Reorder list halves
Implement reorder_list(nums) that returns the first half followed by the reversed second half.
Sort List Merge Sort
Write a function that sorts a list of integers using the merge sort algorithm.
Rotate List Right by k
Implement a function that rotates a list to the right by k positions.
Convert Binary Number List
Given a list of bits (0s and 1s) in most-significant-first order, return the equivalent integer value.
Insertion Sort
Implement insertion sort that sorts a list in-place and returns the same list.
Intersection two lists length
Return the number of distinct elements that appear in both input lists.
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.
Boolean Mask Filter
Write a function that filters a list using a boolean mask and returns the matching elements as a list.
Flatten Multidimensional Lists
Write a function that flattens arbitrarily nested lists of integers into a single list.
Concatenate Horizontally
Write a function that horizontally concatenates two 2D lists into a new 2D list.
Rolling Window Mean
Given a list of numbers and a window size k, return a list of the means of every contiguous subarray of length k.
Linear Interpolation Array
Given an array with some None values, replace them by linear interpolation between the nearest known values.
One Hot Encode Labels
Given a list of categorical labels, return a list of one-hot encoded vectors based on the sort order of unique labels.
Convolve 1D Signal
Write a function that computes the 1D convolution of two lists in 'full' mode.
Average Salary by Department
Given a list of employee tuples (name, department, salary), return a dictionary mapping each department to its average salary.
Pad array edges
Implement a function that pads a list on both ends with a given value to a specified total length.
Showing 49–71 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.