Swap nodes in a linked list without swapping data | Java program to swap two given nodes of a linked list ; head of list ; Function to swap Nodes x and y in linked list by changing links ; Nothing to do if x and y are same ; Search for x ( keep track of prevX and CurrX ) ; Search for y ( keep track of prevY and currY ) ; If either x or y is not present , nothing to do ; If x is not head of linked list ; make y the new head ; If y is not head of linked list ; make x the new head ; Swap next pointers ; Function to add Node at beginning of list . ; 1. alloc the Node and put the data ; 2. Make next of new Node as head ; 3. Move the head to point to new Node ; This function prints contents of linked list starting from the given Node ; Driver program to test above function ; The constructed linked list is : 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7
class Node { int data ; Node next ; Node ( int d ) { data = d ; next = null ; } } class LinkedList { Node head ; public void swapNodes ( int x , int y ) { if ( x == y ) return ; Node prevX = null , currX = head ; while ( currX != null && currX . data != x ) { prevX = currX ; currX = currX . next ; } Node prevY = null , currY = head ; while ( currY != null && currY . data != y ) { prevY = currY ; currY = currY . next ; } if ( currX == null currY == null ) return ; if ( prevX != null ) prevX . next = currY ; else head = currY ; if ( prevY != null ) prevY . next = currX ; else head = currX ; Node temp = currX . next ; currX . next = currY . next ; currY . next = temp ; } 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 ( ) ; llist . push ( 7 ) ; llist . push ( 6 ) ; llist . push ( 5 ) ; llist . push ( 4 ) ; llist . push ( 3 ) ; llist . push ( 2 ) ; llist . push ( 1 ) ; System . out . print ( " Linked list before calling swapNodes ( ) "); llist . printList ( ) ; llist . swapNodes ( 4 , 3 ) ; System . out . print ( " Linked list after calling swapNodes ( ) "); llist . printList ( ) ; } }