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.
Java
// Java program to check length // of a given linklist import java.io.*;class GfG{ // Defining structure static class Node { int data; Node next; }// Function to check the length // of linklist static int LinkedListLength(Node head) { while (head != null && head.next != null) { head = head.next.next; } if (head == null) return 0; return 1; } // Push function static void push(Node head, i nt info) { // Allocating node Node node = new 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 public static void main(String[] args) { 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) { System.out.println("Odd"); } else { System.out.println("Even"); } }} // This code is contributed by Prerna saini |
Output:
Odd
Time Complexity: O(n)
Auxiliary Space: O(1)
Using Recursion
Java
// Java program to check length// of a given linklistimport java.io.*;class GfG{// Defining structurestatic class Node{ int data; Node next;}// Function to check the length// of linkliststatic int LinkedListLength(Node head){ if (head == null) return 0; return 1+LinkedListLength(head.next);} // Push functionstatic void push(Node head, int info){ // Allocating node Node node = new Node(); // Info into node node.data = info; // Next of new node to head node.next = (head); // head points to new node (head) = node;}// Driver codepublic static void main(String[] args){ 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) { System.out.println("Odd"); } else { System.out.println("Even"); }}}// This code is contributed by 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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