Last Occurrence of a Value
Implement a function that returns the last index of a given value in a list, or -1 if it's not present.
Linear Search Implementation
Implement a linear search function that returns the index of the first occurrence of a target in a list, or -1 if not found.
Find all indexes of a substring
Write a function that returns a list of all starting indexes where a substring appears in a string, including overlapping occurrences.
Find substring index
Implement a function that returns the starting index of the first occurrence of a substring using only basic string indexing and slicing.
Index of First Occurrence
Implement a function that finds the starting index of a substring within a string, returning -1 when absent.
Find Missing Number 1 to n
Given a list containing n-1 distinct integers from 1 to n, find the missing number without using extra space.
Insert into a Sorted List
Implement a function that inserts a value into a sorted list at the correct position using binary search.
Find Duplicate Number
Given a list of n+1 integers in the range 1..n, find the one integer that appears more than once.
Last occurrence index
Implement a function that returns the last index of a given value in a list, or -1 if the value is not present.
Binary search
Return the index of target in a sorted list, or -1 if not present.
Longest increasing subsequence
Return the length of the longest strictly increasing subsequence.
Index of peak element
Implement a function that returns the index of any peak element in a given integer array.
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.
Exponential Search
Implement exponential search to find any valid index of a target in a sorted list.
Peak Element in Array
Implement a function that returns the index of any peak element in a list of integers.
K Closest Elements
Implement a function to return the k closest elements to a target in a sorted array.
Trie Insert and Search
Implement a Trie and a scenario runner that executes insert/search/prefix operations.
Jump Search
Implement the jump search algorithm to locate a target in a sorted list, returning its index or -1.
Lowest Common Ancestor in a Binary Search Tree
Implement a function to find the lowest common ancestor of two node values in a binary search tree.
Design Skip List Lite
Implement a simplified skip list supporting insert, search, and delete with O(log n) average complexity.
Knight Tour Count
Implement a backtracking search to count all ways a knight can visit every cell on a 5x5 board exactly once starting from (0,0).
Integer Square Root Floor
Implement a function that returns the greatest integer whose square is ≤ n, using only integer operations.
Integer Square Root
Implement integer_sqrt(n) that returns the largest integer whose square is ≤ n.
Showing 1–24 of 64 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.