Correlation Coefficient
Write a pure-Python function that computes the Pearson correlation coefficient between two lists of numbers.
Z score normalization
Compute the z-scores for a list of numbers using the population standard deviation.
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.
Check Power of Two Bits
Implement is_power_of_two(n) that returns True if n is a power of two and False otherwise.
Single Number XOR
Given a non-empty list of integers where every element appears twice except one, return the single number using XOR.
Missing Number XOR
Given a list of n distinct numbers from 0 to n with one missing, use XOR to find and return the missing number.
Gray Code Encode
Implement a function that converts a non-negative integer to its Gray code representation using bitwise XOR and shift.
Gray Code Decode
Implement gray_decode(n) that converts an n-bit Gray code integer back to its standard binary value using XOR accumulation.
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.
Isolate Rightmost Set Bit
Given an integer, return a number with only its rightmost set bit set.
Rotate Bits Left
Implement a function that rotates the bits of an integer to the left by a specified number of positions.
Bitwise AND of a Range
Given a range [a, b], return the bitwise AND of all integers in that inclusive range without iterating over all numbers.
Add without plus
Implement a function that adds two integers using only bitwise operations, no arithmetic plus or minus.
Divide using shifts
Implement division of two integers using only bit shifts and arithmetic, without using division or modulo operators.
Bit Mask Permissions
Implement helper functions to compose bit masks and check permission bits using bitwise operators.
Set kth Bit
Implement a function that sets the kth bit (0-indexed) of a non-negative integer to 1 and returns the result.
Clear kth Bit
Implement a function that clears the k-th bit of a non-negative integer (turns it to 0) using bitwise operations.
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.
Brian Kernighan count
Implement a function that counts set bits using Brian Kernighan's efficient algorithm.
Reverse Bits
Implement a function that reverses the bits of a given 32-bit unsigned integer.
Swap Odd and Even Bits
Write a function that swaps odd and even bits of a non-negative integer.
Clear Rightmost Set Bit
Write a function clear_rightmost_set_bit that accepts a non-negative integer and returns the integer with its rightmost set bit cleared.
Showing 529–552 of 925 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.