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  1. class Node {
  2.  
  3. 	public int data;
  4. 	public Node next;
  5. 	public Node prev;
  6.  
  7. 	public Node(int data){
  8. 		this.data=data;
  9. 	}
  10.  
  11. 	public String toString(){
  12. 		return ""+data;
  13. 	}
  14. }
  15. /**
  16.  * Recursive Pair swapping in a linked list
  17.  * @author Prateek
  18.  */
  19.  class PairSwapRecursive {
  20. 	/**
  21. 	 * Recursive Subroutine to swap pairs of nodes of linked list
  22. 	 * @return new Head of the linked list
  23. 	 */
  24. 	public Node pairSwap(Node head){
  25. 		Node curr=head;
  26. 		Node front=null;
  27.  
  28. 		if(curr!=null && curr.next!=null){
  29. 			front=curr.next;
  30. 			curr.next = pairSwap(front.next);
  31. 			front.next=curr;
  32. 		}
  33. 		return (front!=null) ? front : curr;
  34. 	}
  35.  
  36. 	public static void main(String[] args) {
  37. 		PairSwapRecursive obj = new PairSwapRecursive() ;
  38.  
  39. 		Node root = new Node(1) ;
  40. 		root.next =new Node(2) ;
  41. 		root.next.next =new Node(3) ;
  42. 		root.next.next.next =new Node(4) ;
  43. 		root.next.next.next.next =new Node(5) ;
  44. 		//root.next.next.next.next.next =new Node(6) ;
  45.  
  46. 		Node head=obj.pairSwap(root);
  47. 		obj.display(head);
  48. 	}
  49.  
  50. 	/**
  51. 	 * Display the nodes of the linked list
  52. 	 */
  53. 	public void display(Node root)	{
  54. 		Node tempNode;
  55. 		tempNode=root;
  56. 		while(tempNode!=null){
  57. 			System.out.print(tempNode.data+"-->");
  58. 			tempNode=tempNode.next;
  59. 		}
  60. 		System.out.print("null");
  61. 		System.out.println();
  62. 	}
  63. }
  64.  
Success #stdin #stdout 0.07s 380224KB
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2-->1-->4-->3-->5-->null
https://ideone.com/3CCIHt
Pair-wise swapping in a Linked List (recursive)
language:
Java (HotSpot 12)
created:
10 years ago
visibility:
public

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