Squares of Sorted Array
Implement a function that returns a sorted list of squares for a given non-decreasing integer array.
Minimum Size Subarray Sum
Given an array of positive integers, return the minimal length of a contiguous subarray with sum at least target, or 0 if none exists.
Fruit into Baskets
Given an array of integers representing fruit types, return the maximum number of fruits you can collect in a contiguous subarray with at most two distinct types.
Longest Substring with At Most K Distinct Characters
Given a string and an integer k, find the length of the longest substring that contains at most k distinct characters.
Trapping Rain Water (Two Pointers)
Given an array of non-negative integers representing elevation heights, compute how much water can be trapped after rain.
Sliding Window Median
Given a list of integers and a positive window size k, return the median of each sliding window of length k.
Longest Repeating Character Replacement
Given a string and an integer k, return the length of the longest substring that can be made of identical characters after at most k replacements.
Remove K Digits Stack
Remove k digits from a non-negative integer string to produce the smallest possible number using a stack-based approach.
Validate Stack Sequences
Given two sequences of distinct integers, verify whether the second sequence is a valid pop order for a stack given the first sequence as push order.
Sum of Subarray Minimums
Given an integer array, sum the minimum of all contiguous subarrays modulo 10^9+7.
Top K Frequent Elements
Given an integer array and a number k, return the k most frequent elements using a heap-based approach.
Kth Largest Element in an Array (Heap Edition)
Implement a function that returns the kth largest element in an unsorted integer array using a heap.
Top K Frequent Elements
Given a list of integers and a number k, return the k most frequent elements in descending order of frequency, with ties broken by larger value.
Find K pairs with smallest sums
Given two sorted arrays and an integer k, return the k smallest pairs (u, v) with the smallest sums, sorted by sum.
Sliding Window Maximum using Heap
Given an array of integers and a window size k, return an array of maximums for each contiguous subarray of length k.
Sum all node values
Add every integer payload in the list.
Maximum node value
Return the largest integer or None when empty.
Merge two sorted lists
Merge two ascending integer lists into one sorted list.
Add Days to Date
Given a date in YYYY-MM-DD format and an integer number of days, return the resulting date in the same format.
Showing 145–163 of 163 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.