Insert a Node at the head of a Linked List


Problem Statement :


Given a pointer to the head of a linked list, insert a new node before the head. The next value in the new node should point to head and the data value should be replaced with a given value. Return a reference to the new head of the list. The head pointer given may be null meaning that the initial list is empty.

Function Description:

Complete the function insertNodeAtHead in the editor below.

insertNodeAtHead has the following parameter(s):
      1. SinglyLinkedListNode llist: a reference to the head of a list
      2. data: the value to insert in the data field of the new node


Input Format:

The first line contains an integer n, the number of elements to be inserted at the head of the list.
The next n lines contain an integer each, the elements to be inserted, one per function call.


Constraints:
      1.   1<=n<=1000
      2.   1<=list[i]<=1000


Solution :



title-img 


                            Solution in C :

In C:

//The following function is all you need to complete the 
// challenge in hackerrank platform

SinglyLinkedListNode* insertNodeAtHead(SinglyLinkedListNode* llist, int data) {
    
    SinglyLinkedListNode* new = malloc(sizeof(SinglyLinkedListNode));
    new->data = data;
    
    if(llist == NULL){
        llist = new;
        new->next = NULL;
        return llist; 
    }
    
    new-> next = llist;
    llist = new;
    return llist;

}







In C++:

//The following function is all you need to complete the challenge 
//in hackerrank platform.

Node* Insert(Node *head,int data)
{
  Node *n = new Node();
  n->data = data;
  n->next=head;
  return head = n;  
}








In Java:

//the following method is all you need to complete the challenge in
//hackerrank platform.

 static SinglyLinkedListNode insertNodeAtHead(SinglyLinkedListNode head, int data) {
        SinglyLinkedListNode node = new SinglyLinkedListNode(data);
        if (head == null) {
            return node;
        } else {
            node.next = head;
            head = node;
            return head;
        }
    }








In Python 3:

# the following method is all that is needed to  complete the 
# challenge in hackerrank platform

def Insert(head, data):
    newNode = Node(data, head)
    
    return newNode








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