Reversing a linked list in python

Question

I am asked to reverse a which takes head as parameter where as head is a linked list e.g.: 1 -> 2 -> 3 which was returned from a function already defined I tried to implemen

Answer 1

I tried a different approach, in place reversal of the LList. Given a list 1,2,3,4

If you successively swap nearby nodes,you'll get the solution.

len=3 (size-1)
2,1,3,4
2,3,1,4
2,3,4,1

len=2 (size-2)
3,2,4,1
3,4,2,1

len=1 (size-3)
4,3,2,1

The code below does just that. Outer for loop successively reduces the len of list to swap between. While loop swaps the data elements of the Nodes.

def Reverse(head):
    temp = head
    llSize = 0
    while temp is not None:
        llSize += 1
        temp = temp.next


    for i in xrange(llSize-1,0,-1):
        xcount = 0
        temp = head
        while (xcount != i):
            temp.data, temp.next.data = temp.next.data, temp.data
            temp = temp.next
            xcount += 1
    return head

This might not be as efficient as other solutions, but helps to see the problem in a different light. Hope you find this useful.