Python Practice Challenges

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

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

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.

Reverse a singly linked list in place and return the new head of the list. You will be given the head of the list.

Given an input string, return the string with its characters in reverse order.

Given an array of integers (`nums`) and a target sum, return the indices of the two numbers that add up to the target. Assume exactly one solution exists.

Calculate the sum and average of all numbers in a given list of integers. Return the result as an object (dictionary) with keys 'sum' and 'average'.

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

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.

Find and return the longest word in a sentence. If there are ties in length, return the first longest word found. The result should be a cleaned word (no punctuation).

Rotate the elements of an array to the left by `k` steps. The rotation should be done in-place or return a new rotated array.

Determine if an input string of parentheses `(`, `)`, `{`, `}`, `[`, `]` is valid. A string is valid if open brackets must be closed by the same type of brackets, and open brackets must be closed in the correct order. Must use a stack data structure.

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.

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

Find the nth term of the Fibonacci sequence, where F(0)=0 and F(1)=1. Optimize for performance using iteration or memoization to avoid redundant calculations.

Given a list of items, return a new list containing only the unique elements in their original order.

Write a function that takes two integer inputs, `a` and `b`, and returns their sum without using the standard '+' or '-' operators. The solution must use bitwise operations.