Week 14 Quiz

Predict, then check: what does this program print?

def countdown(n):
    if n == 0:
        print("Go!")
        return
    print(n)
    countdown(n - 1)

countdown(3)

Select one.

• Go!, then 3, 2, 1, one per line
• 3, 2, 1, then Go!, one per line
• 3, 2, 1, one per line, and nothing else
• 3, 2, 1, 0, then Go!, one per line

Predict, then check: what does this program print?

def factorial(n):
    if n == 0:
        return 1
    return n * factorial(n - 1)

print(factorial(5))

Select one.

• 120
• 24
• 0
• RecursionError

The pinned factorial below prints a line each time a call starts. How many lines that begin with call does factorial(5) print?

def factorial(n, depth=0):
    print("  " * depth + "call factorial(" + str(n) + ")")
    if n == 0:
        print("  " * depth + "return 1")
        return 1
    result = n * factorial(n - 1, depth + 1)
    print("  " * depth + "return " + str(result))
    return result

print(factorial(5))

Select one.

• 4
• 5
• 6
• 120

Predict, then check: what does this program print?

def countup(n):
    if n == 0:
        print("Go!")
        return
    countup(n - 1)
    print(n)

countup(3)

Select one.

• 3, 2, 1, then Go!, one per line
• Go!, then 3, 2, 1, one per line
• 1, 2, 3, then Go!, one per line
• Go!, then 1, 2, 3, one per line

Predict, then check: what is the last line this program prints?

def countdown(n):
    if n == 0:
        print("Go!")
        return
    print(n)
    countdown(n - 1)

result = countdown(3)
print(result)

Select one.

• Go!
• None
• 3
• 0

Predict, then check: what does this program print?

def bad(n):
    return n + bad(n - 1)

print(bad(5))

Select one.

• 15
• 0
• RecursionError
• IndexError

Predict, then check: what does this program print?

def total_pages(daily):
    if daily == []:
        return 0
    return daily[0] + total_pages(daily[1:])

print(total_pages([12, 40, 25, 0, 33, 17, 27]))

Select one.

• 154
• 142
• 22.0
• 0

Select every line this program prints.

def sum_to(n):
    if n == 0:
        return 0
    return n + sum_to(n - 1)

def sum_to_iter(n):
    total = 0
    for i in range(1, n + 1):
        total = total + i
    return total

print(sum_to(5))
print(sum_to_iter(5))
print(sum_to(100))

Select every option that applies.

• 15
• 5050
• 10
• 14
• 4950

In the call countdown(3), what is the 3?

Select one.

• the parameter
• the base case
• the return value
• the argument

True or false: a recursive sum_to whose recursive call passes the same n, as in return n + sum_to(n), still reaches its base case for sum_to(5) as long as the test if n == 0: is present.

True or false.

• True
• False