# Recursive function to pairwise swap elements of a linked list
def pairWiseSwap(head):
# There must be at-least two nodes in the list
if (head != None and head.next != None):
# Swap the node's data with data of next node
swap(head.data, head.next.data);
# Call pairWiseSwap() for rest of the list
pairWiseSwap(head.next.next);
# This code is contributed by _saurabh_jaiswal