Given a singly linked list, write a function to swap elements pairwise.
Input: 1->2->3->4->5->6->NULL Output: 2->1->4->3->6->5->NULL Input: 1->2->3->4->5->NULL Output: 2->1->4->3->5->NULL Input: 1->NULL Output: 1->NULL
For example, if the linked list is 1->2->3->4->5 then the function should change it to 2->1->4->3->5, and if the linked list is then the function should change it to.
METHOD (Iterative):
Start from the head node and traverse the list. While traversing swap data of each node with its next node’s data.
Below is the implementation of the above approach:
# Python program to swap the elements of # linked list pairwise # Node class class Node:
# Constructor to initialize the
# node object
def __init__( self , data):
self .data = data
self . next = None
class LinkedList:
# Function to initialize head
def __init__( self ):
self .head = None
# Function to pairwise swap elements
# of a linked list
def pairwiseSwap( self ):
temp = self .head
# There are no nodes in a
# linked list
if temp is None :
return
# Traverse further only if there
# are at least two left
while (temp and temp. next ):
# If both nodes are same,
# no need to swap data
if (temp.data ! = temp. next .data):
# Swap data of node with its
# next node's data
temp.data, temp. next .data = temp. next .data, temp.data
# Move temp by 2 to the next pair
temp = temp. next . next
# Function to insert a new node at the
# beginning
def push( self , new_data):
new_node = Node(new_data)
new_node. next = self .head
self .head = new_node
# Utility function to print the linked
# LinkedList
def printList( self ):
temp = self .head
while (temp):
print temp.data,
temp = temp. next
# Driver code llist = LinkedList()
llist.push( 5 )
llist.push( 4 )
llist.push( 3 )
llist.push( 2 )
llist.push( 1 )
print "Linked list before calling pairWiseSwap() "
llist.printList() llist.pairwiseSwap() print "Linked list after calling pairWiseSwap()"
llist.printList() # This code is contributed by Nikhil Kumar Singh(nickzuck_007) |
Output:
Linked list before calling pairWiseSwap() 1 2 3 4 5 Linked list after calling pairWiseSwap() 2 1 4 3 5
Time complexity: O(n)
Auxiliary Space: O(1)
Please refer complete article on Pairwise swap elements of a given linked list for more details!