Read the head node value
Return the first value or None when the list is empty.
Read the tail node value
Return the last value or None when the list is empty.
Reverse a linked list copy
Return a new list with node values in reverse order without mutating the input.
Concatenate two linked lists
Append the second list's nodes after the first and return a new list.
Value at index n
Return the value at zero-based index n or None if out of range.
Middle node index
Return the floor middle index for a non-empty list.
Sum all node values
Add every integer payload in the list.
Maximum node value
Return the largest integer or None when empty.
Remove the head node
Return a new list without the first node.
Valid Sudoku Board
Determine if a 9x9 Sudoku board is valid by checking rows, columns, and 3x3 sub-boxes.
Rotate Image 90 Degrees Clockwise
Rotate a square matrix 90 degrees clockwise and return the rotated matrix.
Valid Sudoku Validator
Determine if a given 9x9 Sudoku board is valid by checking rows, columns, and 3x3 boxes.
Toeplitz Matrix Check
Write a function is_toeplitz(matrix) that checks if a 2D list is a Toeplitz matrix, where all elements on the same diagonal from top-left to bottom-right are identical.
Diagonal Traverse Matrix
Implement a function that returns all elements of a matrix in diagonal zigzag order.
Transpose Matrix In-Place
Implement a function that transposes a square matrix in-place and returns the transposed matrix.
Matrix Multiply 2D
Write a function that multiplies two 2D matrices (lists of lists) and returns the product matrix.
Transpose 2D Array
Implement a function that returns the transpose of a rectangular 2D list.
Flipping an Image
Implement a function that flips an image represented as a binary matrix by reversing each row and inverting each pixel.
Days in month
Write a function that returns the number of days in a given month and year, correctly handling leap years.
Format date output
Parse ISO date strings and format them into a friendly US-style date output.
Days Between Dates
Write a function that returns the number of days between two given dates.
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.
Weekday from date
Write a function that returns the full English weekday name for a date string.
Leap Years in Range
Write a function that returns a list of all leap years between two given years, inclusive.
Showing 481–504 of 556 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.