Program To Search An Element In A Singly Linked List

Explanation

In this program, we need to search a node in the given singly linked list.

To solve this problem, we will traverse through the list using a node current. Current points to head and start comparing searched node data with current node data. If they are equal, set the flag to true and print the message along with the position of the searched node.

For, eg. In the above list, a search node says 4 which can be found at the position 4.

Algorithm

Create a class Node which has two attributes: data and next. Next is a pointer to the next node in the list.
Create another class SearchLinkedList which has two attributes: head and tail.
addNode() will add a new node to the list:
1. Create a new node.
2. It first checks, whether the head is equal to null which means the list is empty.
3. If the list is empty, both head and tail will point to a newly added node.
4. If the list is not empty, the new node will be added to end of the list such that tail’s next will point to a newly added node. This new node will become the new tail of the list.
searchNode() will search for a node in the list:
1. Variable i will keep track of the position of the searched node.
2. The variable flag will store boolean value false.
3. Node 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 the searched node. If a match is found, set flag to true.
6. If the flag is true, display the position of the searched node.
7. Else, display the message “Element is not present in the list”.
display() will display the nodes present in the list:
1. Define a node current which will initially point to head of the list.
2. Traverse through the list till current points to null.
3. Display each node by making current to point to node next to it in each iteration.

Solution

Python

  #Represent a node of the singly linked list  class Node:      def __init__(self,data):          self.data = data;          self.next = None;            class SearchLinkedList:      #Represent the head and tail of the singly linked list      def __init__(self):          self.head = None;          self.tail = None;                #addNode() will add a new node to the list      def addNode(self, data):          #Create a new node          newNode = Node(data);                    #Checks if the list is empty          if(self.head == None):              #If list is empty, both head and tail will point to new node              self.head = newNode;              self.tail = newNode;          else:              #newNode will be added after tail such that tail’s next will point to newNode              self.tail.next = newNode;              #newNode will become new tail of the list              self.tail = newNode;                    #searchNode() will search for a given node in the list      def searchNode(self, data):          current = self.head;          i = 1;          flag = False;                    #Checks whether list is empty          if(self.head == None):              print(“List is empty”);          else:              while(current != None):                  #Compares node to be found with each node present in the list                  if(current.data == data):                      flag = True;                      break;                  i=i+1;                  current = current.next;          if(flag):              print(“Element is present in the list at the position : ” + str(i));          else:              print(“Element is not present in the list”);     sList = SearchLinkedList();     #Add nodes to the list  sList.addNode(1);  sList.addNode(2);  sList.addNode(3);  sList.addNode(4);     #Search for node 2 in the list  sList.searchNode(2);  #Search for the node  in the list  sList.searchNode(7);  

Output:

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

C

  #include <stdio.h>  #include <stdbool.h>     //Represent a node of the singly linked list  struct node{      int data;      struct node *next;  };         //Represent the head and tail of the singly linked list  struct node *head, *tail = NULL;     //addNode() will add a new node to the list  void addNode(int data) {      //Create a new node      struct node *newNode = (struct node*)malloc(sizeof(struct node));      newNode->data = data;      newNode->next = NULL;            //Checks if the list is empty      if(head == NULL) {          //If list is empty, both head and tail will point to new node          head = newNode;          tail = newNode;      }      else {          //newNode will be added after tail such that tail’s next will point to newNode          tail->next = newNode;          //newNode will become new tail of the list          tail = newNode;      }  }     //searchNode() will search for a given node in the list  void searchNode(int data) {      struct node *current = head;      int i = 1;      bool flag = false;            //Checks whether list is empty      if(head == NULL) {          printf(“List is empty n”);      }      else {          while(current != NULL) {               //Compares node to be found with each node present in the list              if(current->data == data) {                  flag = true;                  break;              }              i++;              current = current->next;          }      }      if(flag)           printf(“Element is present in the list at the position: %dn”, i);      else           printf(“Element is not present in the listn”);  }        int main()  {      //Add nodes to the list      addNode(1);      addNode(2);      addNode(3);      addNode(4);            //Search for node 2 in the list      searchNode(2);      //Search for node  in the list      searchNode(7);                return 0;  }  

Output:

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

JAVA

  public class SearchLinkedList {            //Represent a node of singly linked list      class Node{          int data;          Node next;                    public Node(int data) {              this.data = data;              this.next = null;          }      }         //Represent the head and tail of the singly linked list      public Node head = null;      public Node tail = null;            //addNode() will add a new node to the list      public void addNode(int data) {          //Create a new node          Node newNode = new Node(data);                    //Checks if the list is empty          if(head == null) {              //If list is empty, both head and tail will point to new node              head = newNode;              tail = newNode;          }          else {              //newNode will be added after tail such that tail’s next will point to newNode              tail.next = newNode;              //newNode will become new tail of the list              tail = newNode;          }      }            //searchNode() will search for a given node in the list      public void searchNode(int data) {          Node current = head;          int i = 1;          boolean flag = false;                    //Checks whether list is empty          if(head == null) {              System.out.println(“List is empty”);          }          else {              while(current != null) {                   //Compares node to be found with each node present in the list                  if(current.data == data) {                      flag = true;                      break;                  }                  i++;                  current = current.next;              }          }          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) {                    SearchLinkedList sList = new SearchLinkedList();                    //Add nodes to the list          sList.addNode(1);          sList.addNode(2);          sList.addNode(3);          sList.addNode(4);                    //Search for node 2 in the list          sList.searchNode(2);          //Search for a node  in the list          sList.searchNode(7);      }  }  

Output:

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

C#

  using System;                        public class CreateList  {      //Represent a node of singly linked list      public class Node<T>{          public T data;          public Node<T> next;                    public Node(T value) {              data = value;              next = null;          }      }                public class SearchLinkedList<T>{          //Represent the head and tail of the singly linked list          public Node<T> head = null;                        public Node<T> tail = null;                //addNode() will add a new node to the list          public void addNode(T data) {              //Create a new node              Node<T> newNode = new Node<T>(data);                 //Checks if the list is empty              if(head == null) {                  //If list is empty, both head and tail will point to new node                  head = newNode;                  tail = newNode;              }              else {                  //newNode will be added after tail such that tail’s next will point to newNode                  tail.next = newNode;                  //newNode will become new tail of the list                  tail = newNode;              }          }                //searchNode() will search for a given node in the list          public void searchNode(T data) {              Node<T> current = head;              int i = 1;              Boolean flag = false;                 //Checks whether list is empty              if(head == null) {                  Console.WriteLine(“List is empty”);              }              else {                  while(current != null) {                       //Compares node to be found with each node present in the list                      if(current.data.Equals(data)) {                          flag = true;                          break;                      }                      i++;                      current = current.next;                  }              }              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()      {          SearchLinkedList<int> sList = new SearchLinkedList<int>();                    //Add nodes to the list          sList.addNode(1);          sList.addNode(2);          sList.addNode(3);          sList.addNode(4);                    //Search for node 2 in the list          sList.searchNode(2);          //Search for a node  in the list          sList.searchNode(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  //Represent a node of singly linked list  class Node{      public $data;      public $next;            function __construct($data){          $this->data = $data;          $this->next = NULL;      }  }  class SearchLinkedList{      //Represent the head and tail of the singly linked list      public $head;      public $tail;      function __construct(){          $this->head = NULL;          $this->tail = NULL;      }            //addNode() will add a new node to the list      function addNode($data) {          //Create a new node          $newNode = new Node($data);                    //Checks if the list is empty          if($this->head == NULL) {              //If list is empty, both head and tail will point to new node              $this->head = $newNode;              $this->tail = $newNode;          }          else {              //newNode will be added after tail such that tail’s next will point to newNode              $this->tail->next = $newNode;              //newNode will become new tail of the list              $this->tail = $newNode;          }      }            //searchNode() will search for a given node in the list      function searchNode($data) {          $current = $this->head;          $i = 1;          $flag = false;                    //Checks whether list is empty          if($this->head == null) {              print(“List is empty<br>”);          }          else {              while($current != null) {                   //Compares node to be found with each node present in the list                  if($current->data == $data) {                      $flag = true;                      break;                  }                  $i++;                  $current = $current->next;              }          }          if($flag)               print(“Element is present in the list at the position : ” . $i);          else               print(“<br>Element is not present in the list”);      }  }        $sList = new SearchLinkedList();            //Add nodes to the list  $sList->addNode(1);  $sList->addNode(2);  $sList->addNode(3);  $sList->addNode(4);     //Search for node 2 in the list  $sList->searchNode(2);  //Search for node  in the list  $sList->searchNode(7);  ?>  </body>  </html>  

Output:

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

Next Topic#

Program To Search An Element In A Singly Linked List

Program to search an element in a singly linked list

Explanation

Algorithm

Solution

Python

C

JAVA

C#

PHP

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