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Recursive approach for alternating split of Linked List
• Difficulty Level : Easy
• Last Updated : 24 Jan, 2020

Given a linked list, split the linked list into two with alternate nodes.

Examples:

```Input : 1 2 3 4 5 6 7
Output : 1 3 5 7
2 4 6

Input : 1 4 5 6
Output : 1 5
4 6
```

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

We have discussed Iterative splitting of linked list.

The idea is to begin from two nodes first and second. Let us call these nodes as ‘a’ and ‘b’. We recurs

## C++

 `// CPP code to split linked list``#include ``using` `namespace` `std;`` ` `// Node structure``struct` `Node {``    ``int` `data;``    ``struct` `Node* next;``};`` ` `// Function to push nodes``// into linked list``void` `push(Node** head, ``int` `new_data)``{``    ``Node* new_node = ``new` `Node;``    ``new_node->data = new_data;``    ``new_node->next = (*head);``    ``(*head) = new_node;``}`` ` `// We basically remove link between 'a'``// and its next. Similarly we remove link``// between 'b' and its next. Then we recur``// for remaining lists.``void` `moveNode(Node* a, Node* b)``{``    ``if` `(b == NULL || a == NULL)``        ``return``;`` ` `    ``if` `(a->next != NULL)``        ``a->next = a->next->next;`` ` `    ``if` `(b->next != NULL)``        ``b->next = b->next->next;`` ` `    ``moveNode(a->next, b->next);``}`` ` `// function to split linked list``void` `alternateSplitLinkedList(Node* head, Node** aRef,``                                        ``Node** bRef)``{``    ``Node* curr = head;``    ``*aRef = curr;``    ``*bRef = curr->next;``    ``moveNode(*aRef, *bRef);``}`` ` `void` `display(Node* head)``{``    ``Node* curr = head;``    ``while` `(curr != NULL) {``        ``printf``(``"%d "``, curr->data);``        ``curr = curr->next;``    ``}``}`` ` `// Driver code``int` `main()``{``    ``Node* head = NULL; ``    ``Node *a = NULL, *b = NULL;`` ` `    ``push(&head, 7);``    ``push(&head, 6);``    ``push(&head, 5);``    ``push(&head, 4);``    ``push(&head, 3);``    ``push(&head, 2);``    ``push(&head, 1);`` ` ` ` `    ``alternateSplitLinkedList(head, &a, &b);`` ` `    ``printf``(``"a : "``);``    ``display(a);``    ``printf``(``"\nb : "``);``    ``display(b);`` ` `    ``return` `0;``}`

## Java

 `// Java code to split linked list``class` `GFG``{``     ` `// Node structure``static` `class` `Node ``{``    ``int` `data;``    ``Node next;``};`` ` `// Function to push nodes``// into linked list``static` `Node push(Node head, ``int` `new_data)``{``    ``Node new_node = ``new` `Node();``    ``new_node.data = new_data;``    ``new_node.next = (head);``    ``(head) = new_node;``    ``return` `head;``}`` ` `static` `Node a = ``null``, b = ``null``;`` ` `// We basically remove link between 'a'``// and its next. Similarly we remove link``// between 'b' and its next. Then we recur``// for remaining lists.``static` `void` `moveNode(Node a, Node b)``{``    ``if` `(b == ``null` `|| a == ``null``)``        ``return``;`` ` `    ``if` `(a.next != ``null``)``        ``a.next = a.next.next;`` ` `    ``if` `(b.next != ``null``)``        ``b.next = b.next.next;`` ` `    ``moveNode(a.next, b.next);``}`` ` `// function to split linked list``static` `void` `alternateSplitLinkedList(Node head)``{``    ``Node curr = head;``    ``a = curr;``    ``b = curr.next;``    ``Node aRef = a, bRef = b;``    ``moveNode(aRef, bRef);``}`` ` `static` `void` `display(Node head)``{``    ``Node curr = head;``    ``while` `(curr != ``null``) ``    ``{``        ``System.out.printf(``"%d "``, curr.data);``        ``curr = curr.next;``    ``}``}`` ` `// Driver code``public` `static` `void` `main(String args[])``{``    ``Node head = ``null``; ``    ``head = push(head, ``7``);``    ``head = push(head, ``6``);``    ``head = push(head, ``5``);``    ``head = push(head, ``4``);``    ``head = push(head, ``3``);``    ``head = push(head, ``2``);``    ``head = push(head, ``1``);``     ` `    ``alternateSplitLinkedList(head);`` ` `    ``System.out.printf(``"a : "``);``    ``display(a);``    ``System.out.printf(``"\nb : "``);``    ``display(b);``}``}`` ` `// This code is contributed by Arnab Kundu`

## Python

 `# Python code to split linked list `` ` `# Node structure ``class` `Node(``object``): ``    ``def` `__init__(``self``, d): ``        ``self``.data ``=` `d ``        ``self``.``next` `=` `None`` ` `# Function to push nodes ``# into linked list ``def` `push( head, new_data) :`` ` `    ``new_node ``=` `Node(``0``) ``    ``new_node.data ``=` `new_data ``    ``new_node.``next` `=` `(head) ``    ``(head) ``=` `new_node ``    ``return` `head `` ` `a ``=` `None``b ``=` `None`` ` `# We basically remove link between 'a' ``# and its next. Similarly we remove link ``# between 'b' and its next. Then we recur ``# for remaining lists. ``def` `moveNode( a, b) :``    ``if` `(b ``=``=` `None` `or` `a ``=``=` `None``) :``        ``return``    ``if` `(a.``next` `!``=` `None``) :``        ``a.``next` `=` `a.``next``.``next``    ``if` `(b.``next` `!``=` `None``) :``        ``b.``next` `=` `b.``next``.``next`` ` `    ``moveNode(a.``next``, b.``next``) `` ` `# function to split linked list ``def` `alternateSplitLinkedList(head) :``     ` `    ``curr ``=` `head``    ``global` `a``    ``global` `b``    ``a ``=` `curr ``    ``b ``=` `curr.``next``    ``aRef ``=` `a``    ``bRef ``=` `b ``    ``moveNode(aRef, bRef) ``    ``return` `head;`` ` `def` `display(head) :`` ` `    ``curr ``=` `head ``    ``while` `(curr !``=` `None``) :``     ` `        ``print``( curr.data,end ``=` `" "``) ``        ``curr ``=` `curr.``next``     ` `# Driver code ``head ``=` `None``head ``=` `push(head, ``7``) ``head ``=` `push(head, ``6``) ``head ``=` `push(head, ``5``) ``head ``=` `push(head, ``4``) ``head ``=` `push(head, ``3``) ``head ``=` `push(head, ``2``) ``head ``=` `push(head, ``1``) ``     ` `head``=``alternateSplitLinkedList(head) `` ` `print``(``"a : "``,end``=``"") ``display(a) ``print``(``"\nb : "``,end``=``"") ``display(b) `` ` `# This code is contributed by Arnab Kundu `

## C#

 `// C# code to split linked list``using` `System;`` ` `class` `GFG``{``     ` `// Node structure``public` `class` `Node ``{``    ``public` `int` `data;``    ``public` `Node next;``};`` ` `// Function to push nodes``// into linked list``static` `Node push(Node head, ``int` `new_data)``{``    ``Node new_node = ``new` `Node();``    ``new_node.data = new_data;``    ``new_node.next = (head);``    ``(head) = new_node;``    ``return` `head;``}`` ` `static` `Node a = ``null``, b = ``null``;`` ` `// We basically remove link between 'a'``// and its next. Similarly we remove link``// between 'b' and its next. Then we recur``// for remaining lists.``static` `void` `moveNode(Node a, Node b)``{``    ``if` `(b == ``null` `|| a == ``null``)``        ``return``;`` ` `    ``if` `(a.next != ``null``)``        ``a.next = a.next.next;`` ` `    ``if` `(b.next != ``null``)``        ``b.next = b.next.next;`` ` `    ``moveNode(a.next, b.next);``}`` ` `// function to split linked list``static` `void` `alternateSplitLinkedList(Node head)``{``    ``Node curr = head;``    ``a = curr;``    ``b = curr.next;``    ``Node aRef = a, bRef = b;``    ``moveNode(aRef, bRef);``}`` ` `static` `void` `display(Node head)``{``    ``Node curr = head;``    ``while` `(curr != ``null``) ``    ``{``        ``Console.Write(``"{0} "``, curr.data);``        ``curr = curr.next;``    ``}``}`` ` `// Driver code``public` `static` `void` `Main(String []args)``{``    ``Node head = ``null``; ``    ``head = push(head, 7);``    ``head = push(head, 6);``    ``head = push(head, 5);``    ``head = push(head, 4);``    ``head = push(head, 3);``    ``head = push(head, 2);``    ``head = push(head, 1);``     ` `    ``alternateSplitLinkedList(head);`` ` `    ``Console.Write(``"a : "``);``    ``display(a);``    ``Console.Write(``"\nb : "``);``    ``display(b);``}``}`` ` `// This code is contributed by PrinciRaj1992`
Output:
```a : 1 3 5 7
b : 2 4 6
```

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