{"id":27590,"date":"2018-04-04T19:32:56","date_gmt":"2018-04-04T14:02:56","guid":{"rendered":"https:\/\/www.wikitechy.com\/technology\/?p=27590"},"modified":"2018-04-04T19:32:56","modified_gmt":"2018-04-04T14:02:56","slug":"c-algorithm-pairwise-swap-elements-given-linked-list","status":"publish","type":"post","link":"https:\/\/www.wikitechy.com\/technology\/c-algorithm-pairwise-swap-elements-given-linked-list\/","title":{"rendered":"C 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
C Programming:<\/strong><\/div>\n
\n
<\/div> 
\/* C program to pairwise swap elements in a given linked list *\/#include<stdio.h>#include<stdlib.h> \/* A linked list node *\/struct node{    int data;    struct node *next;}; \/*Function to swap two integers at addresses a and b *\/void swap(int *a, int *b); \/* Function to pairwise swap elements of a linked list *\/void pairWiseSwap(struct node *head){    struct node *temp = head;     \/* Traverse further only if there are at-least two nodes left *\/    while (temp != NULL && temp->next != NULL)    {        \/* Swap data of node with its next node's data *\/        swap(&temp->data, &temp->next->data);         \/* Move temp by 2 for the next pair *\/        temp = temp->next->next;    }} \/* UTILITY FUNCTIONS *\/\/* Function to swap two integers *\/void swap(int *a, int *b){    int temp;    temp = *a;    *a = *b;    *b = temp;} \/* Function to add a node at the begining of Linked List *\/void push(struct node** head_ref, int new_data){    \/* allocate node *\/    struct node* new_node =              (struct node*) malloc(sizeof(struct node));      \/* put in the data  *\/    new_node->data  = new_data;     \/* link the old list off the new node *\/    new_node->next = (*head_ref);     \/* move the head to point to the new node *\/    (*head_ref)    = new_node;} \/* Function to print nodes in a given linked list *\/void printList(struct node *node){    while (node != NULL)    {        printf("%d ", node->data);       node = node->next;    }} \/* Driver program to test above function *\/int main(){    struct node *start = NULL;     \/* The constructed linked list is:     1->2->3->4->5 *\/    push(&start, 5);    push(&start, 4);    push(&start, 3);    push(&start, 2);    push(&start, 1);     printf("Linked list before calling  pairWiseSwap()\\n");    printList(start);     pairWiseSwap(start);     printf("\\nLinked list after calling  pairWiseSwap()\\n");    printList(start);     return 0;}<\/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
\u00a0C Programming:<\/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":"
C 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-27590","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\/27590","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=27590"}],"version-history":[{"count":0,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/27590\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/media?parent=27590"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/categories?post=27590"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/tags?post=27590"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}