{"id":26936,"date":"2017-12-28T21:43:36","date_gmt":"2017-12-28T16:13:36","guid":{"rendered":"https:\/\/www.wikitechy.com\/technology\/?p=26936"},"modified":"2018-10-29T10:51:20","modified_gmt":"2018-10-29T05:21:20","slug":"java-algorithm-swap-nodes-linked-list-without-swapping-data","status":"publish","type":"post","link":"https:\/\/www.wikitechy.com\/technology\/java-algorithm-swap-nodes-linked-list-without-swapping-data\/","title":{"rendered":"Swap nodes in a linked list without swapping data"},"content":{"rendered":"

Given a linked list<\/a> and two keys in it, swap nodes for two given keys<\/strong>. Nodes should be swapped by changing links. Swapping<\/a> data of nodes may be expensive in many situations when data contains many fields.<\/span><\/p>\n

It may be assumed that all keys in linked list are distinct.<\/p>\n

Examples:<\/strong><\/span><\/h3>\n
Input:  10->15->12->13->20->14,  x = 12, y = 20\r\nOutput: 10->15->20->13->12->14\r\n\r\nInput:  10->15->12->13->20->14,  x = 10, y = 20\r\nOutput: 20->15->12->13->10->14\r\n\r\nInput:  10->15->12->13->20->14,  x = 12, y = 13\r\nOutput: 10->15->13->12->20->14<\/pre>\n
This may look a simple problem, but is interesting question as it has following cases to be handled.
\n1) x and y may or may not be adjacent.
\n2) Either x or y may be a head node.
\n3) Either x or y may be last node.
\n4) x and\/or y may not be present in linked list.<\/p>\n[ad type=”banner”]\n
Let us write a clear working code that handles all the above cases:<\/p>\n
The idea is to first search x and y in given linked list<\/a>. If any of them is not present, then return. While searching for x and y, keep track of current and previous pointers<\/strong>. First change next of previous pointers, then change next of current pointers. Following is Java<\/a> implementation of this approach.<\/p>\n
Java Programming For Swap Nodes in a Linked List:<\/strong><\/span><\/h3>\n
 
 <\/div> 
\/\/ Java program to swap two given nodes of a linked list class Node{    int data;    Node next;    Node(int d)    {        data = d;        next = null;    }} class LinkedList{    Node head; \/\/ head of list     \/* Function to swap Nodes x and y in linked list by       changing links *\/    public void swapNodes(int x, int y)    {        \/\/ Nothing to do if x and y are same        if (x == y) return;         \/\/ Search for x (keep track of prevX and CurrX)        Node prevX = null, currX = head;        while (currX != null && currX.data != x)        {            prevX = currX;            currX = currX.next;        }         \/\/ Search for y (keep track of prevY and currY)        Node prevY = null, currY = head;        while (currY != null && currY.data != y)        {            prevY = currY;            currY = currY.next;        }         \/\/ If either x or y is not present, nothing to do        if (currX == null || currY == null)            return;         \/\/ If x is not head of linked list        if (prevX != null)            prevX.next = currY;        else \/\/make y the new head            head = currY;         \/\/ If y is not head of linked list        if (prevY != null)            prevY.next = currX;        else \/\/ make x the new head            head = currX;        Node temp = currX.next;        currX.next = currY.next;        currY.next = temp;    }     \/* Function to add Node at beginning of list. *\/    public void push(int new_data)    {                Node new_Node = new Node(new_data);         new_Node.next = head;          head = new_Node;    }     public void printList()    {        Node tNode = head;        while (tNode != null)        {            System.out.print(tNode.data+" ");            tNode = tNode.next;        }    }         public static void main(String[] args)    {        LinkedList llist = new LinkedList();         \/* The constructed linked list is:            1->2->3->4->5->6->7 *\/        llist.push(7);        llist.push(6);        llist.push(5);        llist.push(4);        llist.push(3);        llist.push(2);        llist.push(1);         System.out.print("\\n Linked list before calling swapNodes() ");        llist.printList();         llist.swapNodes(4, 3);         System.out.print("\\n Linked list after calling swapNodes() ");        llist.printList();    }}\/\/ This code is contributed by Rajat Mishra<\/code><\/pre> <\/div>\n
Output:<\/strong><\/span><\/h3>\n
 Linked list before calling swapNodes() 1 2 3 4 5 6 7\r\n Linked list after calling swapNodes() 1 2 4 3 5 6 7<\/pre>\n
Optimizations:<\/strong> <\/span><\/h3>\n
The code can be optimized to search x and y in single traversal. Two loops<\/a> are used to keep program simple.<\/p>\n[ad type=”banner”]\n","protected":false},"excerpt":{"rendered":"
Java Algorithm – Swap nodes in a linked list without swapping data – Linked List – Given a linked list and two keys in it, swap nodes for two given keys<\/p>\n","protected":false},"author":1,"featured_media":31615,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[79476,79478],"tags":[80425,80422,80431,80424,80427,80423,80428,80430,80426,80420,80429,80421],"class_list":["post-26936","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-linked-list","category-singly-linked-list","tag-how-to-swap-two-nodes-in-a-doubly-linked-list-java","tag-swap-adjacent-nodes-in-linked-list","tag-swap-adjacent-nodes-in-linked-list-java","tag-swap-alternate-nodes-linked-list","tag-swap-kth-node-from-beginning-with-kth-node-from-end-in-a-linked-list","tag-swap-nodes-doubly-linked-list","tag-swap-nodes-in-doubly-linked-list-java","tag-swap-nodes-in-linked-list","tag-swap-two-adjacent-elements-linked-list-java","tag-swap-two-nodes-in-a-linked-list-java","tag-swapping-two-nodes-in-a-doubly-linked-list-c","tag-write-a-program-to-reverse-a-linked-list"],"_links":{"self":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/26936","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=26936"}],"version-history":[{"count":0,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/posts\/26936\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/media\/31615"}],"wp:attachment":[{"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/media?parent=26936"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/categories?post=26936"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.wikitechy.com\/technology\/wp-json\/wp\/v2\/tags?post=26936"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}