Python Coding Challenges

Extract Hashtags

Extract unique hashtags from a given text string in the order they appear.

strings parsing hashtags

Extract mentions

Extract unique @mentions from a string, respecting email-like patterns and punctuation.

strings parsing sets

Validate time format

Check whether a given string is a valid 24-hour time in HH:MM format.

strings validation time

string-parsing split strip

Parse Log Line

Write a function that parses a log line and returns a dictionary with timestamp, level, and message.

strings whitespace normalization

Replace multiple spaces

Implement a function that replaces every sequence of spaces with a single space.

Remove HTML tags

Remove all HTML tags from a string to extract clean text.

html string parsing

Extract Quoted Strings

Write a function that extracts the text inside every double-quoted substring from a given string.

strings parsing quotes

strings parsing camelcase

Split on camelCase

Given a camelCase string, split it into words at uppercase letters and return them as lowercase words.

Extract domain from URL

Extract the domain (hostname without port or www) from a given URL string.

url parsing strings

strings whitespace split-join

Normalize Whitespace

Write a function that normalizes any whitespace in a string to single spaces and trims the ends.

+5 pts 10m

Strip Leading Zeros

Write a function that strips leading zeros from a string representing a non-negative integer.

strings strip lstrip

+5 pts 5m

parsing strings dictionaries

Parse key=value pairs

Implement a parser that converts a space-separated 'key=value' string into a Python dictionary, supporting quoted values.

Find all numbers in text

Write a function that extracts all standalone integers from a text string using regular expressions.

regex parsing numbers

strings parsing file-paths

Extract file extensions

Implement a function that extracts the extension from a filename according to standard rules.

strings validation returns

Validate username format

Implement a function that validates a username according to length, allowed characters, and no consecutive underscores.

string-manipulation parsing template

Replace template variables

Implement a function that replaces {{variable}} placeholders in a string using a dictionary, leaving unknown placeholders intact.

strings character-comparison distance

Hamming Distance

Implement a function that computes the Hamming distance between two strings of equal length.

Hex encode decode

Write hex_encode and hex_decode to convert between hex strings and integer byte values.

hex encoding strings

strings cipher transformation

ROT13 Transform

Implement ROT13, a letter substitution cipher that rotates the alphabet by 13 positions.

Caesar Cipher Decrypt

Implement a function that decrypts a Caesar cipher by shifting letters back by a given number.

strings ascii cipher

parsing string expression

Strings & Text medium

Simplify Path

Implement a function that simplifies a Unix-style absolute file path to its canonical form.

strings stack parsing

+20 pts 25m

Strings & Text hard

Basic Calculator III

Implement a recursive descent parser to evaluate a fully parenthesized arithmetic expression with +, -, *, / and parentheses.

+45 pts 40m

Strings & Text medium

Minimum Remove Valid Parentheses

Given a string with parentheses and letters, remove the fewest parentheses to make it valid.

strings stack validation

+20 pts 25m

strings deduplication order-preserving

Remove Duplicate Letters

Implement a function that removes duplicate characters from a string while preserving the order of their first occurrence.