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1. What does this print? It uses the lesson's add_two_numbers, from_digits and to_list helpers. ``

python
print(to_list(add_two_numbers(from_digits(9, 9), from_digits(1))))

``

[1, 0, 0][0, 0][9, 9, 1][0, 0, 1]

2. What does this print? ``

python
print(to_list(add_two_numbers(from_digits(9, 9, 9, 9, 9, 9, 9), from_digits(9, 9, 9, 9))))

``

[8, 9, 9, 9, 0, 0, 0][1, 0, 0, 0, 9, 9, 9, 8][8, 9, 9, 9, 0, 0, 0, 1][0, 0, 0, 1, 8, 9, 9, 9]

3. What does this print? It uses the lesson's rotate_right helper, with from_values and to_list. ``

python
print(to_list(rotate_right(from_values(1, 2, 3, 4, 5), 7)))

``

[1, 2, 3, 4, 5][4, 5, 1, 2, 3][2, 3, 4, 5, 1][3, 4, 5, 1, 2]

4. This loop is meant to add two digit lists. What does it return for 99 + 1, and what is wrong? ``

python
while a is not None or b is not None:
    total = carry
    if a is not None:
        total += a.val
        a = a.next
    if b is not None:
        total += b.val
        b = b.next
    tail.next = ListNode(total % 10)
    tail = tail.next
    carry = total // 10

``

[0, 0, 1], and nothing is wrong[1, 0], because the carry is written before the digit[0, 0], because the loop stops before the final carry of 1 is written[0, 0], because the loop reads b.val after b has ended

5. This line replaces the two if checks in the add loop. What happens when it runs for 342 + 65, and why? ``

python
total = a.val + b.val + carry

``

It writes a wrong digit with no error, because a.val is always 0It adds the carry twice, so the answer is one digit too longIt raises AttributeError in the third column, because b is None and None has no valIt raises TypeError in the first column, because Python cannot add two nodes

Digit lists and pair swaps in Python