# Print alternate nodes of a linked list using recursion

Examples :

```Input : 1 -> 2 -> 3 -> 4 -> 5 -> 6 -> 7 -> 8 -> 9 -> 10
Output : 1 -> 3 -> 5 -> 7 -> 9

Input : 10 -> 9
Output : 10
```

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

Recursive Approach :
1. Initialize a static variable(say flag)
2. If flag is odd print the node
3. increase head and flag by 1, and recurse for next nodes.

## C++

 `// CPP code to print alternate nodes ` `// of a linked list using recursion ` `#include ` `using` `namespace` `std; ` ` `  `// A linked list node ` `struct` `Node { ` `    ``int` `data; ` `    ``struct` `Node* next; ` `}; ` ` `  `// Inserting node at the beginning ` `void` `push(``struct` `Node** head_ref, ``int` `new_data) ` `{  ` `    ``struct` `Node* new_node =  ` `       ``(``struct` `Node*)``malloc``(``sizeof``(``struct` `Node)); ` `    ``new_node->data = new_data; ` `    ``new_node->next = (*head_ref); ` `    ``(*head_ref) = new_node; ` `} ` ` `  `// Function to print alternate nodes of linked list. ` `// The boolean flag isOdd is used to find if the current ` `// node is even or odd. ` `void` `printAlternate(``struct` `Node* node, ``bool` `isOdd=``true``) ` `{ ` `    ``if` `(node == NULL) ` `       ``return``; ` `    ``if` `(isOdd == ``true``) ` `        ``cout << node->data << ``" "``;  ` `    ``printAlternate(node->next, !isOdd); ` `} ` ` `  `// Driver code ` `int` `main() ` `{ ` `    ``// Start with the empty list ` `    ``struct` `Node* head = NULL; ` ` `  `    ``// construct below list ` `    ``// 1->2->3->4->5->6->7->8->9->10 ` ` `  `    ``push(&head, 10); ` `    ``push(&head, 9); ` `    ``push(&head, 8); ` `    ``push(&head, 7); ` `    ``push(&head, 6); ` `    ``push(&head, 5); ` `    ``push(&head, 4); ` `    ``push(&head, 3); ` `    ``push(&head, 2); ` `    ``push(&head, 1); ` ` `  `    ``printAlternate(head); ` ` `  `    ``return` `0; ` `} `

## Java

 `// Java code to print alternate nodes  ` `// of a linked list using recursion  ` `class` `GFG  ` `{ ` ` `  `// A linked list node  ` `static` `class` `Node  ` `{  ` `    ``int` `data;  ` `    ``Node next;  ` `};  ` ` `  `// Inserting node at the beginning  ` `static` `Node push( Node head_ref, ``int` `new_data)  ` `{  ` `    ``Node new_node = ``new` `Node();  ` `    ``new_node.data = new_data;  ` `    ``new_node.next = (head_ref);  ` `    ``(head_ref) = new_node;  ` `    ``return` `head_ref; ` `}  ` ` `  `// Function to print alternate nodes of linked list.  ` `// The boolean flag isOdd is used to find if the current  ` `// node is even or odd.  ` `static` `void` `printAlternate( Node node, ``boolean` `isOdd)  ` `{  ` `    ``if` `(node == ``null``)  ` `    ``return``;  ` `    ``if` `(isOdd == ``true``)  ` `        ``System.out.print( node.data + ``" "``);  ` `    ``printAlternate(node.next, !isOdd);  ` `}  ` ` `  `// Driver code  ` `public` `static` `void` `main(String args[]) ` `{  ` `    ``// Start with the empty list  ` `    ``Node head = ``null``;  ` ` `  `    ``// con below list  ` `    ``// 1.2.3.4.5.6.7.8.9.10  ` ` `  `    ``head = push(head, ``10``);  ` `    ``head = push(head, ``9``);  ` `    ``head = push(head, ``8``);  ` `    ``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``);  ` ` `  `    ``printAlternate(head,``true``);  ` ` `  `} ` `} ` ` `  `// This code is contributed by Arnab Kundu `

## Python3

 `# Python3 code to print alternate nodes  ` `# of a linked list using recursion  ` ` `  `# A linked list node ` `class` `Node:  ` `    ``def` `__init__(``self``, data):  ` `        ``self``.data ``=` `data  ` `        ``self``.``next` `=` `None` ` `  `# Inserting node at the beginning  ` `def` `push( head_ref, new_data): ` ` `  `    ``new_node ``=` `Node(new_data); ` `    ``new_node.data ``=` `new_data;  ` `    ``new_node.``next` `=` `head_ref;  ` `    ``head_ref ``=` `new_node;  ` `    ``return` `head_ref;  ` ` `  `# Function to print alternate nodes of  ` `# linked list. The boolean flag isOdd  ` `# is used to find if the current node ` `# is even or odd.  ` `def` `printAlternate( node, isOdd): ` `    ``if` `(node ``=``=` `None``): ` `        ``return``;  ` `    ``if` `(isOdd ``=``=` `True``): ` `        ``print``( node.data, end ``=` `" "``);  ` `    ``if` `(isOdd ``=``=` `True``): ` `        ``isOdd ``=` `False``; ` `    ``else``: ` `        ``isOdd ``=` `True``; ` `    ``printAlternate(node.``next``, isOdd);  ` ` `  `# Driver code  ` ` `  `# Start with the empty list  ` `head ``=` `None``;  ` ` `  `# con below list  ` `# 1->2->3->4->5->6->7->8->9->10  ` `head ``=` `push(head, ``10``);  ` `head ``=` `push(head, ``9``);  ` `head ``=` `push(head, ``8``);  ` `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``);  ` ` `  `printAlternate(head, ``True``);  ` ` `  `# This code is contributed by 29AjayKumar `

## C#

 `// C# code to print alternate nodes  ` `// of a linked list using recursion  ` `using` `System; ` ` `  `class` `GFG  ` `{ ` `  `  `// A linked list node  ` `public` `class` `Node  ` `{  ` `    ``public` `int` `data;  ` `    ``public` `Node next;  ` `};  ` `  `  `// Inserting node at the beginning  ` `static` `Node push( Node head_ref, ``int` `new_data)  ` `{  ` `    ``Node new_node = ``new` `Node();  ` `    ``new_node.data = new_data;  ` `    ``new_node.next = (head_ref);  ` `    ``(head_ref) = new_node;  ` `    ``return` `head_ref; ` `}  ` `  `  `// Function to print alternate nodes of linked list.  ` `// The boolean flag isOdd is used to find if the current  ` `// node is even or odd.  ` `static` `void` `printAlternate( Node node, ``bool` `isOdd)  ` `{  ` `    ``if` `(node == ``null``)  ` `    ``return``;  ` `    ``if` `(isOdd == ``true``)  ` `        ``Console.Write( node.data + ``" "``);  ` `    ``printAlternate(node.next, !isOdd);  ` `}  ` `  `  `// Driver code  ` `public` `static` `void` `Main(String []args) ` `{  ` `    ``// Start with the empty list  ` `    ``Node head = ``null``;  ` `  `  `    ``// con below list  ` `    ``// 1.2.3.4.5.6.7.8.9.10  ` `  `  `    ``head = push(head, 10);  ` `    ``head = push(head, 9);  ` `    ``head = push(head, 8);  ` `    ``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);  ` `  `  `    ``printAlternate(head,``true``);  ` `  `  `} ` `} ` ` `  `// This code has been contributed by 29AjayKumar `

Output:

```1 3 5 7 9
```

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