Calculate the area of a circle given its radius (`r`). Use $\pi \approx 3.14159$. Round the result to two decimal places.

Implement the binary search algorithm to efficiently find a target value in a sorted array. Return the index of the target, or -1 if the target is not found.

Convert a temperature from Celsius (`C`) to Fahrenheit (`F`). Formula: $F = C \times 9/5 + 32$. Return the result as an integer.

Determine if a given string is a palindrome (reads the same forwards and backwards, ignoring case and non-alphanumeric characters).

Write a function that counts and returns the number of vowels (a, e, i, o, u) in a given string. Case should not matter.

Given a string of text, return an object/map where keys are words and values are the frequency (count) of those words. Words should be lowercased and cleaned of punctuation.

Calculate the factorial of a non-negative integer `n` using recursion. The factorial of a number is the product of all integers from 1 to that number.