Remove Consecutive Duplicate Letters
Implement a function that removes consecutive duplicate letters from a string, keeping only one occurrence of each run.
Sort characters alphabetically
Sort all characters in a string alphabetically and return the sorted string.
Replace Spaces with Dashes
Write a function that replaces every space in a string with a dash.
Camel Case Converter
Write a function that converts a space-separated phrase into lower camelCase.
Replace template variables
Implement a function that replaces {{variable}} placeholders in a string using a dictionary, leaving unknown placeholders intact.
Multiply without multiply
Write a function that multiplies two integers using only addition, subtraction, and bit shifts — no * operator.
Count Set Bits
Implement a function that returns the number of set bits (1s) in the binary representation of a non-negative integer.
Single Number XOR
Given a non-empty list of integers where every element appears twice except one, return the single number using XOR.
Gray Code Decode
Implement gray_decode(n) that converts an n-bit Gray code integer back to its standard binary value using XOR accumulation.
Find Rightmost Set Bit
Implement a function that returns the 1-indexed position of the rightmost set bit of a positive integer, or 0 if none.
Isolate Rightmost Set Bit
Given an integer, return a number with only its rightmost set bit set.
Rotate Bits Left
Implement a function that rotates the bits of an integer to the left by a specified number of positions.
Set kth Bit
Implement a function that sets the kth bit (0-indexed) of a non-negative integer to 1 and returns the result.
Compress Bits Run
Write a function that compresses a binary string by representing consecutive identical bits as a count-bit pair.
Brian Kernighan count
Implement a function that counts set bits using Brian Kernighan's efficient algorithm.
Showing 15 challenges · easy
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.