Program to Search an Element in a Circular Linked List

Q. Program to search an element in a circular linked list.

Explanation

In this program, we create a circular linked list and search a node in the list.

9->5->2->7->3

Consider, above example. Suppose we need to search for node 5. To solve this problem, we will iterate through the list and compare each node with 5. If match is found, we will set the flag to true and prints out the position of the node 5. In this example, node 5 is present at the position 2.

Algorithm

Define a Node class which represents a node in the list. It has two properties data and next which will point to the next node.
Define another class for creating circular linked list and it has two nodes: head and tail.
search() will search for a node in the list:
1. Variable i will keep track of the position of the searched node.
2. Variable flag will store boolean value false.
3. Current will point to head node.
4. Iterate through the loop by incrementing current to current.next and i to i + 1.
5. Compare each node's data with searched node. If match is found, set flag to true.
6. If flag is true, prints the position of searched node.
7. Else, print the message "Element is not present in the list".

Solution

Python

#Represents the node of list.
class Node:
    def __init__(self,data):
        self.data = data;
        self.next = None;
 
class CreateList:
    #Declaring head and tail pointer as null.
    def __init__(self):
        self.head = Node(None);
        self.tail = Node(None);
        self.head.next = self.tail;
        self.tail.next = self.head;
    
    #This function will add the new node at the end of the list.
    def add(self,data):
        newNode = Node(data);
        #Checks if the list is empty.
        if self.head.data is None:
            #If list is empty, both head and tail would point to new node.
            self.head = newNode;
            self.tail = newNode;
            newNode.next = self.head;
        else:
            #tail will point to new node.
            self.tail.next = newNode;
            #New node will become new tail.
            self.tail = newNode;
            #Since, it is circular linked list tail will point to head.
            self.tail.next = self.head;
            
    #Searches for a node in the list
    def search(self,element):
        current = self.head;
        i = 1;
        flag = False;
        #Checks whether list is empty
        if(self.head == None):
            print("List is empty");
        else:
            while(True): 
                #Compares element to be found with each node present in the list
                if(current.data ==  element):
                    flag = True;
                    break;
                current = current.next;
                i = i + 1;
                if(current == self.head):
                    break;
            if(flag):
                print("Element is present in the list at the position :  " + str(i));
            else:
                print("Element is not present in the list");
 
class CircularLinkedList:
    cl = CreateList();
    #Adds data to the list
    cl.add(1);
    cl.add(2);
    cl.add(3);
    cl.add(4);
    #Search for node 2 in the list
    cl.search(2);
    #Search for node in the list
    cl.search(7);

Output:

Element is present in the list at the position : 2
Element is not present in the list

C

#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <stdbool.h> 
 
//Represents the node of list.
struct node{
    int data;
    struct node *next;
};
 
//Declaring head and tail pointer as null.
struct node *head = NULL;
struct node *tail = NULL;
 
//This function will add the new node at the end of the list.
void add(int data){
    //Create new node
    struct node *newNode = (struct node*)malloc(sizeof(struct node));
    newNode->data = data;
    //Checks if the list is empty.
    if(head == NULL){
        //If list is empty, both head and tail would point to new node.
        head = newNode;
        tail = newNode;
        newNode->next = head;
    }else {
        //tail will point to new node.
        tail->next = newNode;
        //New node will become new tail.
        tail = newNode;
        //Since, it is circular linked list tail will point to head.
        tail->next = head;
    }
}
 
//Searches for a node in the list
void search(int element) {
    struct node *current = head;
    int i = 1;
    bool flag = false;
    //Checks whether list is empty
    if(head == NULL) {
        printf("List is empty");
    }
    else {
         do{
             //Compares element to be found with each node present in the list
            if(current->data ==  element) {
                flag = true;
                break;
            }
            current = current->next;
            i++;
        }while(current != head);
         if(flag)
            printf("Element is present in the list at the position : %d", i);
        else
            printf("\nElement is not present in the list");
    }
}
    
int main()
{
    //Adds data to the list
   add(1);
   add(2);
   add(3);
   add(4);
   //Search for node 2 in the list
   search(2);
   //Search for node in the list
   search(7);
   
   return 0;
}

Output:

Element is present in the list at the position : 2
Element is not present in the list

JAVA

public class SearchNode {
    //Represents the node of list.
    public class Node{
        int data;
        Node next;
        public Node(int data) {
            this.data = data;
        }
    }
    
    //Declaring head and tail pointer as null.
    public Node head = null;
    public Node tail = null;
    
    //This function will add the new node at the end of the list.
    public void add(int data){
        //Create new node
        Node newNode = new Node(data);
        //Checks if the list is empty.
        if(head == null) {
             //If list is empty, both head and tail would point to new node.
            head = newNode;
            tail = newNode;
            newNode.next = head;
        }
        else {
            //tail will point to new node.
            tail.next = newNode;
            //New node will become new tail.
            tail = newNode;
            //Since, it is circular linked list tail will point to head.
            tail.next = head;
        }
    }
    
    //Searches for a node in the list
    public void search(int element) {
        Node current = head;
        int i = 1;
        boolean flag = false;
        //Checks whether list is empty
        if(head == null) {
            System.out.println("List is empty");
        }
        else {
             do{
                 //Compares element to be found with each node present in the list
                if(current.data ==  element) {
                    flag = true;
                    break;
                }
                current = current.next;
                i++;
            }while(current != head);
             if(flag)
                 System.out.println("Element is present in the list at the position : " + i);
            else
                 System.out.println("Element is not present in the list");
        }
    }
    
    public static void main(String[] args) {
        SearchNode cl = new SearchNode();
        //Adds data to the list
        cl.add(1);
        cl.add(2);
        cl.add(3);
        cl.add(4);
        //Search for node 2 in the list
        cl.search(2);
        //Search for node in the list
        cl.search(7);
    }
}

Output:

Element is present in the list at the position : 2
Element is not present in the list

C#

 using System; 
namespace CircularLinkedList 
{                     
    public class Program
    {
        //Represents the node of list.
        public class Node<T>{
            public T data;
            public Node<T> next;
            public Node(T value) {
                data = value;
                next = null;
            }
        }
        
        public class CreateList<T>{
            protected Node<T> head = null;             
             protected Node<T> tail = null;
            
            //This function will add the new node at the end of the list.
            public void add(T data){
                //Create new node
                Node<T> newNode = new Node<T>(data);
                //Checks if the list is empty.
                if(head == null){
                    head = newNode;
                    tail = newNode;
                    newNode.next = head;
                }else{
                    //tail will point to new node.
                    tail.next = newNode;
                    //New node will become new tail.
                    tail = newNode;
                    //Since, it is circular linked list tail will point to head.
                    tail.next = head;
                }
            }
        
            //Searches for a node in the list
            public void search(T element) {
                Node<T> current = head;
                int i = 1;
                bool flag = false;
                //Checks whether list is empty
                if(head == null) {
                    Console.WriteLine("List is empty");
                }
                else {
                     do{
                         //Compares element to be found with each node present in the list
                        if(current.data.Equals(element)) {
                            flag = true;
                            break;
                        }
                        current = current.next;
                        i++;
                    }while(current != head);
                     if(flag)
                         Console.WriteLine("Element is present in the list at the position : " + i);
                    else
                         Console.WriteLine("Element is not present in the list");
                }
            }
        }
        
        public static void Main()
        {
            
        CreateList<int> cl = new CreateList<int>();
        //Adds data to the list
        cl.add(1);
        cl.add(2);
        cl.add(3);
        cl.add(4);
        //Search for node 2 in the list
        cl.search(2);
        //Search for node in the list
        cl.search(7);
        }    
    }
}

Output:

Element is present in the list at the position : 2
Element is not present in the list

PHP

<!DOCTYPE html>
<html>
<body>
<?php
//Represents the node of list.
class Node{
    public $data;
    public $next;
    function __construct($data){
        $this->data = $data;
        $this->next = NULL;
    }
}
class CreateList{
    //Declaring head and tail pointer as null.
    private $head;
    private $tail;
    function __construct(){
        $this->head = NULL;
        $this->tail = NULL;
    }
    //This function will add the new node at the end of the list.
    function add($data){
        //Create new node
        $newNode = new Node($data);
        //Checks if the list is empty.
        if($this->head == NULL){
            //If list is empty, both head and tail would point to new node.
            $this->head = $newNode;
            $this->tail = $newNode;
            $newNode->next = $this->head;
        }
        else{
            //tail will point to new node.
            $this->tail->next = $newNode;
            //New node will become new tail.
            $this->tail = $newNode;
            //Since, it is circular linked list tail will point to head.
            $this->tail->next = $this->head;
        }
    }
    
    //Searches for a node in the list
    function search($element) {
        $current = $this->head;
        $i = 1;
        $flag = false;
        //Checks whether list is empty
        if($this->head == NULL) {
            echo "List is empty";
        }
        else {
             do{
                 //Compares element to be found with each node present in the list
                if($current->data == $element) {
                    $flag = true;
                    break;
                }
                $current = $current->next;
                $i++;
            }while($current != $this->head);
             if($flag)
                 echo "Element is present in the list at the position : $i <br>";
            else
                 echo "Element is not present in the list<br>";
        }
    }
}
 
$cl = new CreateList();
//Adds data to the list
$cl->add(1);
$cl->add(2);
$cl->add(3);
$cl->add(4);
//Search for node 2 in the list
$cl->search(2);
//Search for node  in the list
$cl->search(7);
?>
</body>
</html>

Output:

Element is present in the list at the position : 2
Element is not present in the list

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