How can I write a recursive function to reverse a linked list?

Question

I am looking to do it with Python. And I don\'t want to just print it in reverse, but actually reverse the given nodes. I have seen it done in other languages but had trouble fi

Answer 1

def reverse (item, tail = None):
    next = item.next
    item.next = tail
    if next is None:
        return item
    else:
        return reverse(next, item)

Using such a simple linked list implementation:

class LinkedList:
    def __init__ (self, value, next = None):
        self.value = value
        self.next = next
    def __repr__ (self):
        return 'LinkedList({}, {})'.format(self.value, repr(self.next))

Example:

>>> a = LinkedList(1, LinkedList(2, LinkedList(3, LinkedList(4))))
>>> a
LinkedList(1, LinkedList(2, LinkedList(3, LinkedList(4, None))))
>>> b = reverse(a)
>>> b
LinkedList(4, LinkedList(3, LinkedList(2, LinkedList(1, None))))
>>> a # note that there is a new head pointer now
LinkedList(1, None)