Search an element in a Linked List (Iterative and Recursive)

Write a function that searches a given key ‘x’ in a given singly linked list. The function should return true if x is present in linked list and false otherwise.

   bool search(Node *head, int x)

For example, if the key to be searched is 15 and linked list is 14->21->11->30->10, then function should return false. If key to be searched is 14, then the function should return true.

Iterative Solution

2) Initialize a node pointer, current = head.
3) Do following while current is not NULL
    a) current->key is equal to the key being searched return true.
    b) current = current->next
4) Return false

Following is iterative implementation of above algorithm to search a given key.

C++

// Iterative C++ program to search  
// an element in linked list  
#include <bits/stdc++.h> 
using namespace std;  
  
/* Link list node */
class Node  
{  
    public: 
    int key;  
    Node* next;  
};  
  
/* Given a reference (pointer to pointer) to the head  
of a list and an int, push a new node on the front  
of the list. */
void push(Node** head_ref, int new_key)  
{  
    /* allocate node */
    Node* new_node = new Node(); 
  
    /* put in the key */
    new_node->key = new_key;  
  
    /* link the old list off the new node */
    new_node->next = (*head_ref);  
  
    /* move the head to point to the new node */
    (*head_ref) = new_node;  
}  
  
/* Checks whether the value x is present in linked list */
bool search(Node* head, int x)  
{  
    Node* current = head; // Initialize current  
    while (current != NULL)  
    {  
        if (current->key == x)  
            return true;  
        current = current->next;  
    }  
    return false;  
}  
  
/* Driver program to test count function*/
int main()  
{  
    /* Start with the empty list */
    Node* head = NULL;  
    int x = 21;  
  
    /* Use push() to construct below list  
    14->21->11->30->10 */
    push(&head, 10);  
    push(&head, 30);  
    push(&head, 11);  
    push(&head, 21);  
    push(&head, 14);  
  
    search(head, 21)? cout<<"Yes" : cout<<"No";  
    return 0;  
}  
  
// This is code is contributed by rathbhupendra 

C

// Iterative C program to search an element in linked list 
#include<stdio.h> 
#include<stdlib.h> 
#include<stdbool.h> 
  
/* Link list node */
struct Node 
{ 
    int key; 
    struct Node* next; 
}; 
  
/* Given a reference (pointer to pointer) to the head 
  of a list and an int, push a new node on the front 
  of the list. */
void push(struct Node** head_ref, int new_key) 
{ 
    /* allocate node */
    struct Node* new_node = 
            (struct Node*) malloc(sizeof(struct Node)); 
  
    /* put in the key  */
    new_node->key  = new_key; 
  
    /* link the old list off the new node */
    new_node->next = (*head_ref); 
  
    /* move the head to point to the new node */
    (*head_ref)    = new_node; 
} 
  
/* Checks whether the value x is present in linked list */
bool search(struct Node* head, int x) 
{ 
    struct Node* current = head;  // Initialize current 
    while (current != NULL) 
    { 
        if (current->key == x) 
            return true; 
        current = current->next; 
    } 
    return false; 
} 
  
/* Driver program to test count function*/
int main() 
{ 
    /* Start with the empty list */
    struct Node* head = NULL; 
    int x = 21; 
  
    /* Use push() to construct below list 
     14->21->11->30->10  */
    push(&head, 10); 
    push(&head, 30); 
    push(&head, 11); 
    push(&head, 21); 
    push(&head, 14); 
  
    search(head, 21)? printf("Yes") : printf("No"); 
    return 0; 
} 

Java

// Iterative Java program to search an element 
// in linked list 
  
//Node class 
class Node 
{ 
    int data; 
    Node next; 
    Node(int d) 
    { 
        data = d; 
        next = null; 
    } 
} 
  
//Linked list class 
class LinkedList 
{ 
    Node head;    //Head of list 
  
    //Inserts a new node at the front of the list 
    public void push(int new_data) 
    { 
        //Allocate new node and putting data 
        Node new_node = new Node(new_data); 
  
        //Make next of new node as head 
        new_node.next = head; 
  
        //Move the head to point to new Node 
        head = new_node; 
    } 
  
    //Checks whether the value x is present in linked list 
    public boolean search(Node head, int x) 
    { 
        Node current = head;    //Initialize current 
        while (current != null) 
        { 
            if (current.data == x) 
                return true;    //data found 
            current = current.next; 
        } 
        return false;    //data not found 
    } 
  
    //Driver function to test the above functions 
    public static void main(String args[]) 
    { 
  
        //Start with the empty list 
        LinkedList llist = new LinkedList(); 
  
        /*Use push() to construct below list 
        14->21->11->30->10  */
        llist.push(10); 
        llist.push(30); 
        llist.push(11); 
        llist.push(21); 
        llist.push(14); 
  
        if (llist.search(llist.head, 21)) 
            System.out.println("Yes"); 
        else
            System.out.println("No"); 
    } 
} 
// This code is contributed by Pratik Agarwal 

Python

# Iterative Python program to search an element 
# in linked list 
  
# Node class 
class Node: 
      
    # Function to initialise the node object 
    def __init__(self, data): 
        self.data = data # Assign data 
        self.next = None # Initialize next as null 
  
# Linked List class 
class LinkedList: 
    def __init__(self): 
        self.head = None # Initialize head as None 
  
    # This function insert a new node at the 
    # beginning of the linked list 
    def push(self, new_data): 
      
        # Create a new Node 
        new_node = Node(new_data) 
  
        # 3. Make next of new Node as head 
        new_node.next = self.head 
  
        # 4. Move the head to point to new Node 
        self.head = new_node 
  
    # This Function checks whether the value 
    # x present in the linked list  
    def search(self, x): 
  
        # Initialize current to head 
        current = self.head 
  
        # loop till current not equal to None 
        while current != None: 
            if current.data == x: 
                return True # data found 
              
            current = current.next
          
        return False # Data Not found 
  
  
# Code execution starts here 
if __name__ == '__main__': 
  
    # Start with the empty list 
    llist = LinkedList() 
  
    ''' Use push() to construct below list 
        14->21->11->30->10 '''
    llist.push(10); 
    llist.push(30); 
    llist.push(11); 
    llist.push(21); 
    llist.push(14); 
  
    if llist.search(21): 
        print("Yes") 
    else: 
        print("No") 
  
# This code is contributed by Ravi Shankar 

C#

// Iterative C# program to search an element 
// in linked list 
using System; 
  
// Node class 
public class Node 
{ 
    public int data; 
    public Node next; 
    public Node(int d) 
    { 
        data = d; 
        next = null; 
    } 
} 
  
// Linked list class 
public class LinkedList 
{ 
    Node head; // Head of list 
  
    // Inserts a new node at the front of the list 
    public void push(int new_data) 
    { 
        // Allocate new node and putting data 
        Node new_node = new Node(new_data); 
  
        // Make next of new node as head 
        new_node.next = head; 
  
        // Move the head to point to new Node 
        head = new_node; 
    } 
  
    // Checks whether the value x is present in linked list 
    public bool search(Node head, int x) 
    { 
        Node current = head; // Initialize current 
        while (current != null) 
        { 
            if (current.data == x) 
                return true; // data found 
            current = current.next; 
        } 
        return false; // data not found 
    } 
  
    // Driver code 
    public static void Main(String []args) 
    { 
  
        // Start with the empty list 
        LinkedList llist = new LinkedList(); 
  
        /*Use push() to construct below list 
        14->21->11->30->10 */
        llist.push(10); 
        llist.push(30); 
        llist.push(11); 
        llist.push(21); 
        llist.push(14); 
  
        if (llist.search(llist.head, 21)) 
            Console.WriteLine("Yes"); 
        else
            Console.WriteLine("No"); 
    } 
} 
  
// This code contributed by Rajput-Ji 

Output:

Yes

Recursive Solution

bool search(head, x)
1) If head is NULL, return false.
2) If head's key is same as x, return true;
2) Else return search(head->next, x)

Following is recursive implementation of above algorithm to search a given key.

C

// Recursive C program to search an element in linked list 
#include<stdio.h> 
#include<stdlib.h> 
#include<stdbool.h> 
/* Link list node */
struct Node 
{ 
    int key; 
    struct Node* next; 
}; 
  
/* Given a reference (pointer to pointer) to the head 
  of a list and an int, push a new node on the front 
  of the list. */
void push(struct Node** head_ref, int new_key) 
{ 
    /* allocate node */
    struct Node* new_node = 
            (struct Node*) malloc(sizeof(struct Node)); 
  
    /* put in the key  */
    new_node->key  = new_key; 
  
    /* link the old list off the new node */
    new_node->next = (*head_ref); 
  
    /* move the head to point to the new node */
    (*head_ref)    = new_node; 
} 
  
/* Checks whether the value x is present in linked list */
bool search(struct Node* head, int x) 
{ 
    // Base case 
    if (head == NULL) 
        return false; 
      
    // If key is present in current node, return true 
    if (head->key == x) 
        return true; 
  
    // Recur for remaining list 
    return search(head->next, x); 
} 
  
/* Driver program to test count function*/
int main() 
{ 
    /* Start with the empty list */
    struct Node* head = NULL; 
    int x = 21; 
  
    /* Use push() to construct below list 
     14->21->11->30->10  */
    push(&head, 10); 
    push(&head, 30); 
    push(&head, 11); 
    push(&head, 21); 
    push(&head, 14); 
  
    search(head, 21)? printf("Yes") : printf("No"); 
    return 0; 
} 

Java

// Recursive Java program to search an element 
// in linked list 
  
  
// Node class 
class Node 
{ 
    int data; 
    Node next; 
    Node(int d) 
    { 
        data = d; 
        next = null; 
    } 
} 
  
// Linked list class 
class LinkedList 
{ 
    Node head;    //Head of list 
  
    //Inserts a new node at the front of the list 
    public void push(int new_data) 
    { 
        //Allocate new node and putting data 
        Node new_node = new Node(new_data); 
  
        //Make next of new node as head 
        new_node.next = head; 
  
        //Move the head to point to new Node 
        head = new_node; 
    } 
  
    // Checks whether the value x is present 
    // in linked list 
    public boolean search(Node head, int x) 
    { 
        // Base case 
        if (head == null) 
            return false; 
  
        // If key is present in current node, 
        // return true 
        if (head.data == x) 
            return true; 
  
        // Recur for remaining list 
        return search(head.next, x); 
    } 
  
    // Driver function to test the above functions 
    public static void main(String args[]) 
    { 
        // Start with the empty list 
        LinkedList llist = new LinkedList(); 
  
        /* Use push() to construct below list 
           14->21->11->30->10  */
        llist.push(10); 
        llist.push(30); 
        llist.push(11); 
        llist.push(21); 
        llist.push(14); 
  
        if (llist.search(llist.head, 21)) 
            System.out.println("Yes"); 
        else
            System.out.println("No"); 
    } 
} 
// This code is contributed by Pratik Agarwal 

Output:

Yes

Python

# Recursive Python program to  
# search an element in linked list 
  
# Node class 
class Node: 
      
    # Function to initialise  
    # the node object 
    def __init__(self, data): 
        self.data = data # Assign data 
        self.next = None # Initialize next as null 
  
class LinkedList: 
      
    def __init__(self): 
        self.head = None # Initialize head as None 
  
    # This function insert a new node at  
    # the beginning of the linked list 
    def push(self, new_data): 
      
        # Create a new Node 
        new_node = Node(new_data) 
  
        # Make next of new Node as head 
        new_node.next = self.head 
  
        # Move the head to  
        # point to new Node 
        self.head = new_node 
      
      
    # Checks whether the value key  
    # is present in linked list  
    def search(self, li, key): 
          
        # Base case 
        if(not li): 
            return False
          
        # If key is present in  
        # current node, return true 
        if(li.data == key): 
            return True
          
        # Recur for remaining list 
        return self.search(li.next, key) 
      
# Driver Code             
if __name__=='__main__': 
  
    li = LinkedList() 
      
    li.push(1) 
    li.push(2) 
    li.push(3) 
    li.push(4) 
      
    key = 4
      
    if li.search(li.head,key): 
        print("Yes") 
    else: 
        print("No") 
      
# This code is contributed 
# by Manoj Sharma 

C#

// Recursive C# program to search  
// an element in linked list 
using System; 
  
// Node class 
public class Node 
{ 
    public int data; 
    public Node next; 
    public Node(int d) 
    { 
        data = d; 
        next = null; 
    } 
} 
  
// Linked list class 
public class LinkedList 
{ 
    Node head; //Head of list 
  
    //Inserts a new node at the front of the list 
    public void push(int new_data) 
    { 
        //Allocate new node and putting data 
        Node new_node = new Node(new_data); 
  
        //Make next of new node as head 
        new_node.next = head; 
  
        //Move the head to point to new Node 
        head = new_node; 
    } 
  
    // Checks whether the value x is present 
    // in linked list 
    public bool search(Node head, int x) 
    { 
        // Base case 
        if (head == null) 
            return false; 
  
        // If key is present in current node, 
        // return true 
        if (head.data == x) 
            return true; 
  
        // Recur for remaining list 
        return search(head.next, x); 
    } 
  
    // Driver code 
    public static void Main() 
    { 
        // Start with the empty list 
        LinkedList llist = new LinkedList(); 
  
        /* Use push() to construct below list 
        14->21->11->30->10 */
        llist.push(10); 
        llist.push(30); 
        llist.push(11); 
        llist.push(21); 
        llist.push(14); 
  
        if (llist.search(llist.head, 21)) 
            Console.WriteLine("Yes"); 
        else
            Console.WriteLine("No"); 
    } 
} 
  
// This code is contributed by PrinciRaj1992 

Output:

Yes

This article is contributed by Ravi. Please write comments if you find anything incorrect, or you want to share more information about the topic discussed above

My Personal Notes

Suggest a Topic

C++

C

Java

Python

C#

C

Java

Python

C#

Recommended Posts: