Same Tree Check
Write a function that checks whether two binary trees are identical in structure and node values.
Cycle Detection in Undirected Graph
Write a function that detects if an undirected graph contains a cycle.
Find center of star graph
Write a function that finds the center node of a star graph from its list of edges in O(1) time.
Wildcard Match (Simple)
Write a function that checks whether a string matches a pattern with '*' and '?' wildcards.
Permutation Generator
Write a function that returns all permutations of a list of distinct integers.
Permutations
Write a function that returns every permutation of the elements in the input list.
Power set from set
Write a function to return the power set of a given list of distinct elements.
Upper Bound Binary Search
Write a function that returns the index of the first element greater than a target in a sorted list.
First Bad Version
Implement a function to find the first bad version in a sorted range using binary search.
Longest Substring Without Repeating Characters
Implement a function that returns the length of the longest substring without repeating characters.
Squares of Sorted Array
Implement a function that returns a sorted list of squares for a given non-decreasing integer array.
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.
Days Between Dates
Write a function that returns the number of days between two given dates.
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.
Unix timestamp to datetime
Write a function that returns a UTC datetime string from a Unix timestamp.
Next Weekday Finder
Write a function that returns the next weekday date after a given date.
Duration Human Readable
Write a function that turns a number of seconds into a human-readable duration like '2 hours, 1 minute'.
Showing 241–264 of 286 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.