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Problem 4: Reverse (50pts)

Problem

my_reverse takes in a list l and returns a new list that contains exactly the same elements in l but in the reverse order.

my_reverse 接受一个列表 l，并返回一个包含与 l 中完全相同的元素但顺序相反的新列表。

def my_reverse(l):
    """Returns a new list that contains the exact same elements in l with reversed order.
    >>> a = ['S', 'I', 'C', 'P']
    >>> a is my_reverse(a) # the returned list is newly created
    False
    >>> my_reverse(my_reverse(a)) == a # reverse twice equals to the original list
    True
    >>> my_reverse(a)
    ['P', 'C', 'I', 'S']
    >>> a
    ['S', 'I', 'C', 'P']
    """
    "*** YOUR CODE HERE ***"

Hints

Hint: use clever slicing.

  • 使用巧妙的切片（slicing）。

  • 切片能接受三个参数，想想怎么用第三个参数。

Solutions

使用切片，step = -1。

def my_reverse(l):
    return l[::-1]