Question

Python

Mutable Sequences

Implement a function reverse that takes a list as an argument and reverses the list. You should mutate the original list, without creating any new lists. Do NOT return anything. Do not use any built-in list functions such as reverse().

def reverse(lst):

   """Reverses lst in place (i.e. doesn't create new lists).

    >>> L = [1, 2, 3, 4]

    >>> reverse(L)

    >>> L

    [4, 3, 2, 1]

    """

Answer 1

def reverse(lst):
    """Reverses lst in place (i.e. doesn't create new lists).
     >>> L = [1, 2, 3, 4]
     >>> reverse(L)
     >>> L
     [4, 3, 2, 1]
     """
    for i in range(len(lst) // 2):
        lst[i], lst[len(lst) - i - 1] = lst[len(lst) - i - 1], lst[i]


# Testing the function here. ignore/remove the code below if not required
L = [1, 2, 3, 4]
print(L)
reverse(L)
print(L)
L = [1, 2, 3, 4, 5]
print(L)
reverse(L)
print(L)