Basic Calculator III
Implement a recursive descent parser to evaluate a fully parenthesized arithmetic expression with +, -, *, / and parentheses.
Word ladder length
Return the length of the shortest transformation from beginWord to endWord changing one letter at a time.
Match IPv6 Address
Write a function that uses a regex to validate whether a string is a fully expanded IPv6 address.
Palindrome Partitioning Minimum Cuts
Given a string, return the minimum number of cuts needed such that every substring in the partition is a palindrome.
Remove invalid parentheses
Given a string with parentheses and letters, return all valid strings after removing the minimum number of invalid parentheses.
Remove K Digits to Form the Smallest Number
Given a non-negative integer as a string, remove exactly k digits to form the smallest possible integer without leading zeros.
Minimum Window Substring
Implement a sliding window algorithm to find the minimum window substring containing all characters of a given pattern.
Minimum Window Subsequence
Given strings s and t, return the minimum window substring of s that contains t as a subsequence, or empty string if none exists.
Join node values with arrows
Format string node values as 'a -> b -> c'; empty list returns ''.
Showing 1–9 of 9 challenges · hard
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.