# C Program To Check Whether The Length Of Given Linked List Is Even Or Odd

Last Updated : 24 Jan, 2023

Given a linked list, the task is to make a function which checks whether the length of the linked list is even or odd.

Examples:

```Input: 1->2->3->4->NULL
Output: Even

Input: 1->2->3->4->5->NULL
Output: Odd```

Method 1: Count the codes linearly
Traverse the entire Linked List and keep counting the number of nodes. As soon as the loop is finished, we can check if the count is even or odd. You may try it yourself.
Method 2: Stepping 2 nodes at a time
Approach:

```1. Take a pointer and move that pointer two nodes at a time
2. At the end, if the pointer is NULL then length is Even, else Odd.```

## C

 `// C program to check length ` `// of a given linklist` `#include` `#include`   `// Defining structure` `struct` `Node` `{` `    ``int` `data;` `    ``struct` `Node* next;` `};`   `// Function to check the length ` `// of linklist` `int` `LinkedListLength(``struct` `Node* head)` `{` `    ``while` `(head && head->next)` `    ``{` `        ``head = head->next->next;` `    ``}` `    ``if` `(!head)` `        ``return` `0;` `    ``return` `1;` `}` `    `  `// Push function` `void` `push(``struct` `Node** head, ` `          ``int` `info)` `{` `    ``// Allocating node` `    ``struct` `Node* node = ` `          ``(``struct` `Node*) ``malloc``(``sizeof``(``struct` `Node));` `    `  `    ``// Info into node` `    ``node->data = info;` `    `  `    ``// Next of new node to head` `    ``node->next = (*head);`   `    ``// head points to new node` `    ``(*head) = node;` `}`   `// Driver code` `int` `main(``void``)` `{` `    ``struct` `Node* head = NULL;` `    `  `    ``// Adding elements to Linked ` `    ``// List` `    ``push(&head, 4);` `    ``push(&head, 5);` `    ``push(&head, 7);` `    ``push(&head, 2);` `    ``push(&head, 9);` `    ``push(&head, 6);` `    ``push(&head, 1);` `    ``push(&head, 2);` `    ``push(&head, 0);` `    ``push(&head, 5);` `    ``push(&head, 5);` `    ``int` `check = ` `        ``LinkedListLength(head);` `    `  `    ``// Checking for length of` `    ``// linklist` `    ``if``(check == 0)` `    ``{` `        ``printf``(``"Even"``);` `    ``}` `    ``else` `    ``{` `        ``printf``(``"Odd"``);` `    ``}` `    ``return` `0;` `}`

Output:

`Odd`

Time Complexity: O(n)
Auxiliary Space: O(1)

## C

 `// C program to check length` `// of a given linklist` `#include` `#include`   `// Defining structure` `struct` `Node` `{` `    ``int` `data;` `    ``struct` `Node* next;` `};`   `// Function to check the length` `// of linklist` `int` `LinkedListLength(``struct` `Node* head)` `{` `    ``if` `(head == NULL) ``return` `0;` `    ``return` `1+LinkedListLength(head->next);` `}` `    `  `// Push function` `void` `push(``struct` `Node** head,` `        ``int` `info)` `{` `    ``// Allocating node` `    ``struct` `Node* node =` `        ``(``struct` `Node*) ``malloc``(``sizeof``(``struct` `Node));` `    `  `    ``// Info into node` `    ``node->data = info;` `    `  `    ``// Next of new node to head` `    ``node->next = (*head);`   `    ``// head points to new node` `    ``(*head) = node;` `}`   `// Driver code` `int` `main(``void``)` `{` `    ``struct` `Node* head = NULL;` `    `  `    ``// Adding elements to Linked` `    ``// List` `    ``push(&head, 4);` `    ``push(&head, 5);` `    ``push(&head, 7);` `    ``push(&head, 2);` `    ``push(&head, 9);` `    ``push(&head, 6);` `    ``push(&head, 1);` `    ``push(&head, 2);` `    ``push(&head, 0);` `    ``push(&head, 5);` `    ``push(&head, 5);` `    ``int` `check =` `        ``LinkedListLength(head);` `    `  `    ``// Checking for length of` `    ``// linklist` `    ``if``(check == 0)` `    ``{` `        ``printf``(``"Even"``);` `    ``}` `    ``else` `    ``{` `        ``printf``(``"Odd"``);` `    ``}` `    ``return` `0;` `}`   `//This code is contributed Vinay Pinjala.`

Output

`Odd`

Time Complexity: O(n)
Auxiliary Space: O(n)

Please refer complete article on Check whether the length of given linked list is Even or Odd for more details!

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