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

After seeking to thoroughly understand how to reverse a linked list in python using both iterative and recursive methods, and working on an adequate refactoring, I coded this. Many links that I studied seemed slightly unclear or had unnecessary steps. If I have not arrived at the bare minimum / clear steps, I think these are at least close. I felt it best to not include the output, but it will run as is and produce output (python 2.7 and easy to modify for 3.x).

class Node:
def __init__(self,val):
    self.val = val
    self.next = None # the pointer initially points to nothing

def traverse(self):
    # start from the head node
    node = self 
    while node != None:
        # access the node value
        out_string = 'val = %d, loc = %s, next = %s'
        print out_string % (node.val, node, node.next)
        # move on to the next node
        node = node.next 

def reverse_iteratively(self):
    previous = None
    current = None
    head = self

    while head:
        # before reverse
        previous = current
        current = head
        head = head.next
        # reverse the link
        current.next = previous

def reverse_recursively(self, node, pre=None):
    if node.next != None:
        self.reverse_recursively(node.next, pre=node)
    node.next = pre

### Operation Section
node0 = Node(0)
node1 = Node(7);  node0.next = node1
node2 = Node(14); node1.next = node2
node3 = Node(21); node2.next = node3
node4 = Node(28); node3.next = node4
node5 = Node(35); node4.next = node5
node6 = Node(42); node5.next = node6
node7 = Node(49); node6.next = node7
node8 = Node(56); node7.next = node8
node9 = Node(63); node8.next = node9

print "Forward linked:"
node0.traverse()
node0.reverse_recursively(node0)
print "Reverse linked:"
node9.traverse()