Basic Calculator
Implement a function that evaluates a simple arithmetic expression with +, -, *, / and parentheses.
Zigzag string conversion
Encode a string in zigzag order across numRows rows, then read row by row.
Product of All Except Zeros Handling
Given a list of integers, return a list where each element is the product of all other elements, handling zeros correctly.
Two Missing Numbers
Given a list of n-2 unique integers from 1 to n, find the two missing numbers efficiently.
2D Vector dataclass
Implement a Vector2D dataclass with +, -, scalar *, dot product, and magnitude.
Zeller Congruence Weekday
Implement a function that returns the weekday name for a given date using Zeller's congruence.
Extended Euclidean Algorithm
Implement the extended Euclidean algorithm to return (gcd, x, y) such that ax + by = gcd(a, b).
Multinomial coefficient
Write a function to compute the multinomial coefficient efficiently for given nonnegative counts.
Correlation Coefficient
Write a pure-Python function that computes the Pearson correlation coefficient between two lists of numbers.
Bell number
Implement a function to compute the Bell number B(n) using dynamic programming.
Perfect Squares Sum
Given a positive integer n, return the least number of perfect squares (e.g., 1, 4, 9, 16, ...) that sum to n.
Integer Break Product
Given a positive integer n, break it into at least two positive integers that sum to n and maximize their product.
Ugly Number II
Given an integer n, return the nth ugly number using an efficient dynamic programming approach.
Kth Missing Positive
Given a strictly increasing array and an integer k, return the k-th positive integer that is missing from the array.
Minimum Speed to Arrive on Time
Given commute distances and a time limit, compute the minimum integer speed so you arrive on time.
Nth Magical Number
Given three integers n, a, b, return the nth positive integer that is divisible by either a or b.
Maximum Average Pass Ratio
Given class pass/total counts and extra students, maximize the average pass ratio by assigning extra students optimally.
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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.