Recursion Quiz

To pass the quiz, you must correctly answer at least 9 of the 10 questions below. # --quizzes-- ## --quiz-- ### --question-- #### --text-- What is recursion in programming? #### --distractors-- A method of sorting lists. --- A loop that never ends. --- A function that returns `None`. #### --answer-- A process in which a function calls itself. ### --question-- #### --text-- Which of the following is an example of recursion? #### --distractors-- ```py def factorial(n): result = 1 while n > 0: result *= n n -= 1 return result ``` --- ```py def factorial(n): numbers = [number for number in range(1, n + 1)] result = 1 for number in numbers: result *= number return result ``` --- ```py def factorial(n): result = 1 for number in range(n, 0, -1): result *= number return result ``` #### --answer-- ```py def factorial(n): if n == 0 or n == 1: return 1 return n * factorial(n - 1) ``` ### --question-- #### --text-- What will the following function return? ```py def sum_numbers(n): if n == 0: return 0 return n + sum_numbers(n - 1) sum_numbers(3) ``` #### --distractors-- 3 --- 0 --- 1 #### --answer-- 6 ### --question-- #### --text-- How many times will the `mystery` function be called? ```py def mystery(n): if n <= 1: return 1 return mystery(n - 2) mystery(5) ``` #### --distractors-- 2 --- 5 --- 4 #### --answer-- 3 ### --question-- #### --text-- Which of the following is true about recursion? #### --distractors-- It should never have a base case. --- It should only be used for the Fibonacci sequence. --- It should only be used for factorials. #### --answer-- It should always have a base case. ### --question-- #### --text-- Which of the following options would be an appropriate base case for the given example? ```py def count_down_to_zero(number): # Base case goes here. print(number) count_down_to_zero(number - 1) ``` #### --distractors-- ```py if number > 0: return ``` --- ```py if number != 0: return ``` --- ```py if number == 0: return ``` #### --answer-- ```py if number < 0: return ``` ### --question-- #### --text-- Why must recursion have a base case? #### --distractors-- To ensure the function always has a return value. --- To reduce the number of function calls. --- To ensure all recursive calls are executed in the correct order. #### --answer-- To provide a way for the function to stop making recursive calls and avoid a `RecursionError`. ### --question-- #### --text-- What will this recursive function do? ```py def repeat_string(string): return string + repeat_string(string) ``` #### --distractors-- Return the string twice. --- Return `None`. --- Create an empty string. #### --answer-- Raise a `RecursionError`. ### --question-- #### --text-- What is a call stack? #### --distractors-- A list of function calls that have been executed. --- A list of values that were returned by a function. --- A special function used to call a function exactly three times. #### --answer-- A data structure that keeps track of function calls and their execution order. ### --question-- #### --text-- What does this recursive function do? ```py def change_string(string): if string == "": return "" return change_string(string[1:]) + string[0] ``` #### --distractors-- Duplicates a string. --- Removes vowels. --- Removes spaces. #### --answer-- Reverses a string.