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Java Program to Get the middle element of LinkedList in a single iteration
In this article, we will understand how to get the middle element of linkedList in a single iteration. The java.util.LinkedList class operations perform we can expect for a doubly-linked list. Operations that index into the list will traverse the list from the beginning or the end, whichever is closer to the specified index.
Below is a demonstration of the same −
Suppose our input is −
Input linked list: 100 200 330
The desired output would be −
The middle element of the list is: 200
Algorithm
Step 1 - START Step 2 - Declare a LinkedList namely input_list. Declare five node objects namely head, first_node, second_node, pointer_1, pointer_2. Step 3 - Define the values. Step 4 - Using a while loop, iterate over the linked list, get the middle element by traversing the list using pointer_1 and pointer_2 until pointer_1.next is not null. Step 5 - Display the pointer_2 value as result. Step 6 - Stop
Example 1
Here, we bind all the operations together under the ‘main’ function.
public class LinkedList {
Node head;
static class Node {
int value;
Node next;
Node(int d) {
value = d;
next = null;
}
}
public static void main(String[] args) {
LinkedList input_list = new LinkedList();
input_list.head = new Node(100);
Node second_node = new Node(200);
Node third_node = new Node(330);
input_list.head.next = second_node;
second_node.next = third_node;
Node current_node = input_list.head;
System.out.print("The linked list is defined as: " );
while (current_node != null) {
System.out.print(current_node.value + " ");
current_node = current_node.next;
}
Node pointer_1 = input_list.head;
Node pointer_2 = input_list.head;
while (pointer_1.next != null) {
pointer_1 = pointer_1.next;
if(pointer_1.next !=null) {
pointer_1 = pointer_1.next;
pointer_2 = pointer_2.next;
}
}
System.out.println("\nThe middle element of the list is: " + pointer_2.value);
}
}Output
The linked list is defined as: 100 200 330 The middle element of the list is: 200
Example 2
Here, we encapsulate the operations into functions exhibiting object oriented programming.
public class LinkedList {
Node head;
static class Node {
int value;
Node next;
Node(int d) {
value = d;
next = null;
}
}
static void get_middle_item(LinkedList input_list){
Node pointer_1 = input_list.head;
Node pointer_2 = input_list.head;
while (pointer_1.next != null) {
pointer_1 = pointer_1.next;
if(pointer_1.next !=null) {
pointer_1 = pointer_1.next;
pointer_2 = pointer_2.next;
}
}
System.out.println("\nThe middle element of the list is: " + pointer_2.value);
}
public static void main(String[] args) {
LinkedList input_list = new LinkedList();
input_list.head = new Node(100);
Node second_node = new Node(200);
Node third_node = new Node(330);
input_list.head.next = second_node;
second_node.next = third_node;
Node current_node = input_list.head;
System.out.print("The linked list is defined as: " );
while (current_node != null) {
System.out.print(current_node.value + " ");
current_node = current_node.next;
}
get_middle_item(input_list);
}
}Output
The linked list is defined as: 100 200 330 The middle element of the list is: 200
Updated on: 30-Mar-2022
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