{"id":27597,"date":"2018-04-04T19:33:21","date_gmt":"2018-04-04T14:03:21","guid":{"rendered":"https:\/\/www.wikitechy.com\/technology\/?p=27597"},"modified":"2018-04-04T19:33:21","modified_gmt":"2018-04-04T14:03:21","slug":"python-algorithm-pairwise-swap-elements-given-linked-list","status":"publish","type":"post","link":"https:\/\/www.wikitechy.com\/technology\/python-algorithm-pairwise-swap-elements-given-linked-list\/","title":{"rendered":"Python Algorithm – Pairwise swap elements of a given linked list"},"content":{"rendered":"

Given a singly linked list, write a function to swap elements pairwise. 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 1->2->3->4->5->6 then the function should change it to 2->1->4->3->6->5.<\/span><\/p>\n

\u00a0METHOD 1 (Iterative) <\/strong>
\nStart from the head node and traverse the list. While traversing swap data of each node with its next node\u2019s data<\/div>\n
<\/div>\n
Python Programming:<\/strong><\/div>\n
\n
<\/div> 
# 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 ilnked list        if temp is None:            return                  # Traverse furthur only if there are at least two        #  left        while(temp is not None and temp.next is not None):             # Swap data of node with its next node's data            temp.data, temp.next.data = temp.next.data, temp.data                          # Move temo by 2 fro 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 prit the linked LinkedList    def printList(self):        temp = self.head        while(temp):            print temp.data,            temp = temp.next  # Driver programllist = 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  "\\nLinked list after calling pairWiseSwap()"llist.printList() # This code is contributed by Nikhil Kumar Singh(nickzuck_007)<\/code><\/pre> <\/div>\n
Output:<\/strong><\/p>\n
Linked List before calling pairWiseSwap() \r\n1 2 3 4 5 \r\nLinked List after calling pairWiseSwap() \r\n2 1 4 3 5<\/pre>\n
Time complexity: O(n)<\/p>\n
METHOD 2 (Recursive)<\/strong>
\nIf there are 2 or more than 2 nodes in Linked List then swap the first two nodes and recursively call for rest of the list.<\/p>\n
\u00a0Python\u00a0Programming:<\/strong><\/div>\n
\n
 
 <\/div> 
\/* Recursive function to pairwise swap elements of a linked list *\/void pairWiseSwap(struct node *head){  \/* There must be at-least two nodes in the list *\/  if (head != NULL && head->next != NULL)  {      \/* 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);  }  }<\/code><\/pre> <\/div>\n<\/div>\n
Time complexity: O(n)<\/div>\n
<\/div>\n<\/div>\n","protected":false},"excerpt":{"rendered":"
Python Algorithm – Pairwise swap elements of a given linked list – Linked List – Given a singly linked list, write a function to swap elements pairwise<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[79476,79478],"tags":[80425,81794,80431,80424,81791,81792,80430,81793,80420,80421],"class_list":["post-27597","post","type-post","status-publish","format-standard","hentry","category-linked-list","category-singly-linked-list","tag-how-to-swap-two-nodes-in-a-doubly-linked-list-java","tag-reverse-linked-list-in-pairs-java","tag-swap-adjacent-nodes-in-linked-list-java","tag-swap-alternate-nodes-linked-list","tag-swap-list-nodes-in-pairs","tag-swap-nodes-doubly-linked-list-c","tag-swap-nodes-in-linked-list","tag-swap-nodes-in-pairs-java","tag-swap-two-nodes-in-a-linked-list-java","tag-write-a-program-to-reverse-a-linked-list"],"_links":{"self":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/27597","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/comments?post=27597"}],"version-history":[{"count":0,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/27597\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/media?parent=27597"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/categories?post=27597"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/tags?post=27597"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}