Find Missing Number
Given a list of n distinct integers from 0..n with one missing, return the missing number.
Convolve 1D signal
Implement a 1D convolution function with three modes using pure Python.
Jump Game Minimum Jumps
Given an array of non-negative integers where each element is the maximum jump length, compute the minimum jumps to reach the last index.
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.
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.
Showing 1–24 of 121 challenges
Guide: free Python coding challenges
Practice Python by solving problems
PythonSkillset challenges are hands-on coding exercises from beginner to advanced. Open a challenge, read the problem, write Python in the split-pane editor, and run tests with Pyodide — no install required.
How to use the arena
- Pick a category — basics, algorithms, strings, and more
- Open a challenge, read the statement, and edit the starter code
- Run tests, fix failures, then try a related quiz or tutorial lesson
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.