Insert into a Sorted List
Implement a function that inserts a value into a sorted list at the correct position using binary search.
Binary search
Return the index of target in a sorted list, or -1 if not present.
BFS level-order traversal
Return the level-order traversal of a binary tree as a list of lists.
Longest increasing subsequence
Return the length of the longest strictly increasing subsequence.
Find Peak Element
Implement a function that returns the index of any peak element in an integer array.
Median of Two Sorted Arrays
Given two sorted arrays, return the median of the combined sorted array in O(log(min(n,m))) time.
Path Sum II All Paths
Return all root-to-leaf paths where the sum of node values equals a target.
Shortest Path in Binary Matrix
Implement BFS to find the shortest path length from (0,0) to (n-1,n-1) in an n x n binary matrix, moving through 0 cells in 8 directions.
Tree inorder generator
Write a generator function that yields a binary tree's node values in inorder traversal.
Integer Square Root Floor
Implement a function that returns the greatest integer whose square is ≤ n, using only integer operations.
Count Set Bits
Implement a function that returns the number of set bits (1s) in the binary representation of a non-negative integer.
Gray Code Decode
Implement gray_decode(n) that converts an n-bit Gray code integer back to its standard binary value using XOR accumulation.
Compress Bits Run
Write a function that compresses a binary string by representing consecutive identical bits as a count-bit pair.
Sparse Number Check
Check if a non-negative integer is sparse, meaning its binary representation contains no adjacent 1 bits.
Maximal square
Given a 2D binary matrix of 0s and 1s, compute the area of the largest square containing only 1s.
Binary Search Tree Class
Build a BinarySearchTree class and a sequence runner that executes a list of operations.
Binary Tree Inorder Traversal
Implement an inorder traversal function that returns node values in left-root-right order.
Preorder Traversal
Implement a function that returns the preorder traversal values of a binary tree.
Postorder Traversal
Implement a function that returns the postorder traversal of a binary tree as a list of node values.
Maximum depth of tree
Implement max_depth(root) to return the maximum depth of a binary tree.
Minimum Depth of Tree
Given a binary tree, compute the minimum depth from the root to the nearest leaf node.
Symmetric Tree Check
Write a function that checks whether a binary tree is symmetric (a mirror of itself).
Same Tree Check
Write a function that checks whether two binary trees are identical in structure and node values.
Lowest Common Ancestor in a Binary Tree
Implement a function to find the lowest common ancestor (LCA) of two nodes in a binary tree.
Sum Root to Leaf Numbers
Given the root of a binary tree, compute the total sum of all root-to-leaf numbers.
Binary tree left side view
Given a binary tree, return the leftmost node's value at each depth, from top to bottom.
Vertical Order Traversal
Compute the vertical order traversal of a binary tree, grouping nodes by column and row.
Delete Node in BST
Implement a function that deletes a key from a binary search tree and returns the new root.
Insert into BST
Implement insertion into a Binary Search Tree while maintaining BST properties.
Search in Rotated Array
Implement an efficient search in a rotated sorted array using modified binary search.
Interpolation Search
Implement interpolation search in Python on a sorted list of integers.
Ternary Search
Implement ternary search to locate the maximum of a discrete unimodal function.
01 Matrix Nearest Zero
Given a binary matrix, return a matrix of the same shape where each cell contains the Manhattan distance to the nearest 0.
Showing 33 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.