Euler Totient Function
Implement Euler's totient function φ(n) for positive integers.
Perfect Number Check
Write a function that returns True if a number is perfect, i.e., equal to the sum of its proper divisors.
Abundant Number Check
Implement a function to check whether a given integer is abundant: sum of proper divisors exceeds the number.
Amicable Numbers Check
Write a function that checks if two numbers are an amicable pair by comparing sums of proper divisors.
Armstrong Number Check
Implement a function that checks if a given integer is an Armstrong number.
Happy number check
Implement a function that returns True if a number is happy, False otherwise.
Harshad Number Check
Write a function that checks if a number is a Harshad (or Niven) number.
Smith Number Check
Write a function to check if a number is a Smith number by comparing digit sums of the number and its prime factorization.
Triangular Number
Implement a function that returns the nth triangular number using the closed-form formula.
Lucas Sequence
Implement a function to compute the n-th Lucas number using iteration or recursion with memoization.
Partition function
Write a function that returns the number of ways to write a positive integer as a sum of positive integers (order irrelevant).
Multiply without multiply
Write a function that multiplies two integers using only addition, subtraction, and bit shifts — no * operator.
Zeller Congruence Weekday
Implement a function that returns the weekday name for a given date using Zeller's congruence.
Dot Product of Vectors
Implement a function that returns the dot product of two numeric vectors.
Modular Inverse
Implement a function that returns the modular inverse of a modulo m, or -1 if it does not exist.
Polynomial Fit Coefficients
Implement a function that returns the coefficients of the best-fit quadratic polynomial for given points.
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.
Binomial Coefficient
Implement a function to compute binomial coefficients modulo 10^9+7 for n up to 10^5.
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 Encode
Implement a function that converts a non-negative integer to its Gray code representation using bitwise XOR and shift.
Find Rightmost Set Bit
Implement a function that returns the 1-indexed position of the rightmost set bit of a positive integer, or 0 if none.
Rotate Bits Left
Implement a function that rotates the bits of an integer to the left by a specified number of positions.
Add without plus
Implement a function that adds two integers using only bitwise operations, no arithmetic plus or minus.
Showing 241–264 of 365 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.