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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 ""+data;
  13. 	}
  14. }
  15.  
  16.  class ReverseInChunks {
  17. 	public Node reverseInchunks(Node root, int k){
  18.  
  19. 		if(root==null)
  20. 			return null;
  21.  
  22. 		Node first=root;
  23. 		Node current=first;
  24.  
  25. 		int count = k-1;
  26. 		while(current.next!=null && count > 0)
  27. 		{
  28. 			current=current.next;
  29. 			count--;
  30. 		}
  31.  
  32. 		Node  last=reverseInchunks(current.next,k);
  33. 		current.next=null;
  34.  
  35. 		Node subHead=reverse(first);
  36.  
  37. 		first.next=last;
  38.  
  39. 		return subHead;
  40. 	}
  41.  
  42. 	public Node  reverse(Node head) {
  43.  
  44. 		Node result;
  45. 		if(head.next ==null) 
  46. 			return head;
  47.  
  48. 		result = reverse(head.next);
  49.  
  50. 		head.next.next = head;
  51.  
  52. 		head.next = null;
  53.  
  54. 		return result;
  55. 	}
  56.  
  57. 	public void displayList(Node root)
  58. 	{
  59.  
  60. 		Node temp=root;
  61. 		while(temp!=null)
  62. 		{
  63. 			System.out.print(temp.data+"-->");
  64. 			temp=temp.next;
  65. 		}
  66. 		System.out.print("null");
  67. 		System.out.println();
  68. 	}
  69.  
  70. 	public Node reverseChunkIterative(Node head, int k){
  71.  
  72. 		if(head==null)
  73. 			return null;
  74.  
  75. 		Node first, previous,last;
  76. 		first= previous=last=null;
  77.  
  78. 		Node current=head;
  79.  
  80. 		while(current!=null){
  81.  
  82.  
  83. 			Node temp=current; 
  84. 			previous =null;
  85.             Node next=null;
  86.             int count =k;
  87.  
  88. 			while(current!=null  && count>0){
  89. 				next = current.next;
  90. 				current.next = previous ;
  91. 				previous = current ;
  92. 				current = next;
  93. 				count--;
  94. 			}
  95.  
  96. 			if(first == null)
  97. 				first = previous;
  98. 			else
  99. 				last.next=previous;
  100.  
  101. 			last=temp;
  102. 		}
  103. 		return first;
  104. 	}
  105.  
  106. 	public static void main(String[] args) {
  107. 		Node head= new Node(1);
  108. 		head.next= new Node(2);
  109. 		head.next.next= new Node(3);
  110. 		head.next.next.next= new Node(4);
  111. 		head.next.next.next.next= new Node(5);
  112. 		head.next.next.next.next.next= new Node(6);
  113. 		head.next.next.next.next.next.next= new Node(7);
  114. 		//head.next.next.next.next.next.next.next= new LNode(8);
  115.  
  116. 		ReverseInChunks obj=new ReverseInChunks();
  117. 		System.out.println("Before: ");
  118. 		obj.displayList(head);
  119. 		Node r=obj.reverseInchunks(head, 3);
  120. 		//LNode r=obj.reverseChunkIterative(head, 3);
  121. 		System.out.println("After: ");
  122. 		obj.displayList(r);
  123.  
  124. 	}
  125. }
  126.  
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-->null
After: 
3-->2-->1-->6-->5-->4-->7-->null
https://ideone.com/YjACJU
language:
Java (12.0.1)
created:
10 years ago
visibility:
secret

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