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  1. class Node {
  2.  
  3. 	public Node prev;
  4. 	public int data;
  5. 	public Node next;
  6.  
  7. 	public Node(int data)	{
  8. 		this.data=data;
  9. 	}
  10.  
  11. 	public String toString(){
  12. 		return ""+this.data ;
  13. 	}
  14. }
  15. /**
  16.  * Reverse Alternative chunks in the linked list
  17.  * @author Prateek
  18.  */
  19.  
  20.  class ReverseAlternativeChunk {
  21.  
  22. 	public Node reverseAlternativeChunks(Node root, int k , boolean flag){
  23.  
  24. 	  if(root==null)
  25. 	   return null;
  26.  
  27. 	  Node first=root;
  28. 	  Node current=first;
  29.  
  30. 	  int count = k-1;
  31. 	  while(current.next!=null && count > 0)
  32. 	  {
  33. 	   current=current.next;
  34. 	   count--;
  35. 	  }
  36.  
  37. 	  Node  last=reverseAlternativeChunks(current.next,k , !flag);
  38. 	  current.next=null;
  39.  
  40. 	  Node subHead = null;
  41. 	  if(flag){
  42. 		  subHead=reverse(first);
  43. 		  first.next=last;
  44. 	  }
  45. 	  else
  46. 	  {
  47. 		  subHead = first;
  48. 		  current.next=last;
  49. 	  }
  50.  
  51. 	  return subHead;
  52. 	 }
  53.  
  54. 	 public Node  reverse(Node head) {
  55.  
  56. 	  Node result;
  57. 	  if(head.next ==null) 
  58. 	   return head;
  59.  
  60. 	  result = reverse(head.next);
  61.  
  62. 	  head.next.next = head;
  63.  
  64. 	  head.next = null;
  65.  
  66. 	  return result;
  67. 	 }
  68.  
  69. 	 public void displayList(Node head)
  70. 		{
  71. 			Node tempNode;
  72. 			tempNode=head;
  73. 			while(tempNode!=null)
  74. 			{
  75. 				System.out.print(tempNode.data+"-->");
  76. 				tempNode=tempNode.next;
  77. 			}
  78. 			System.out.print("null");
  79. 			System.out.println();
  80. 		}
  81.  
  82.  
  83.  
  84. 	 public static void main(String[] args) {
  85. 		 Node head= new Node(1);
  86. 			head.next= new Node(2);
  87. 			head.next.next= new Node(3);
  88. 			head.next.next.next= new Node(4);
  89. 			head.next.next.next.next= new Node(5);
  90. 			head.next.next.next.next.next= new Node(6);
  91. 			head.next.next.next.next.next.next= new Node(7);
  92. 			head.next.next.next.next.next.next.next= new Node(8);
  93.  
  94. 			ReverseAlternativeChunk obj=new ReverseAlternativeChunk();
  95. 			System.out.println("Before: ");
  96. 			obj.displayList(head);
  97. 			Node r=obj.reverseAlternativeChunks(head, 3 , true);
  98. 			System.out.println("After: ");
  99. 			obj.displayList(r);
  100. 	}
  101. }
  102.  
Success #stdin #stdout 0.07s 380160KB
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stdin
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Standard input is empty
stdout
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Before: 
1-->2-->3-->4-->5-->6-->7-->8-->null
After: 
3-->2-->1-->4-->5-->6-->8-->7-->null
https://ideone.com/7BDUIt
language:
Java (12.0.1)
created:
10 years ago
visibility:
secret

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