Python Review Module 14 - Recursion

If the base condition is not defined in the recursive function, _____.

• the program runs only once

• the program runs as many times as the number passed as its argument

• the program terminates giving an error

• the program gets into an infinite loop

What is output?

def divide_by_two(count):

if count == 1:

print('Terminated..!')

else:

print(count)

divide_by_two(count/2)

divide_by_two(9)

• 9

  4.5

  2.25

  1.125

  Terminated..!

• 9

  4.5

  2.25

  Terminated..!

• Infinite loop

• 9

  4.5

  2.25

  1.125

  0.5625

  Terminated..!

Assume that there is a recursive binary search function find(). If a sorted list has a data structure with indices 0 to 50 and the item being searched for happens to be at location 6, write each call of find() that would occur while searching for that item. The first is find(0,50).

• find(0, 25) find(0, 12) find(0, 6)

• find(0, 25) find(0, 12)

• find(0, 25)

• find(0, 25) find(0, 12) find(0, 6) find(0, 3)

Which is the best way to debug recursive functions?

• Adding print statement of what that line of code does.

• Adding output statements by keeping all the statements left aligned

• Adding output statements with an indent to print statements at every iteration.

• Adding output statements by keeping all the statements equally indented

While adding output statements to debug recursive functions, _____ the print statements to show the current depth of recursion.

• left align

• indent

• right align

• center align

An indent variable _____ number of spaces on each iteration.

• adds unequal

• removes unequal

• removes equal

• adds equal

What is the role of sys.getrecursionlimit()?

• It measures the maximum depth of the function.

• It changes the depth of the function.

• It isolates the defined function

• It finds the error of the function.

Which of the following is a good candidate for using recursive functions?

• To solve the greatest common divisor (GCD) problem

• To solve problems that have a true and false solution

• To solve problems that require excessive memory allocation

• To solve logarithmic problems

Which code calculates the power of a number raised to another (a^b)?

• def power(a,b):

  if b == 1:

  return a

  else:

  return a**power(a,b-1)

• def power(a,b):

  if b == 1:

  return a

  else:

  return a*power(b-1,a)

• def power(a,b):

  if b == 1:

  return a

  else:

  return a**power(b-1,a)

• def power(a,b):

  if b == 1:

  return a

  else:

  return a*power(a,b-1)

Identify the error in the code that scrambles a word’s letters in all the possible ways..

def scramble(r_letters, s_letters):

if len(r_letters) == 0:

print(s_letters)

else:

for i in range(len(r_letters)):

scramble_letter = r_letters[i]

remaining_letters = r_letters[:i] + r_letters[i-1:]

scramble(remaining_letters, s_letters + scramble_letter)

scramble('abc','')

• scramble_letter = r_letters[i]

• remaining_letters = r_letters[:i] + r_letters[i-1:]

• scramble(remaining_letters, s_letters + scramble_letter)

• if len(r_letters) == 0