FIFA-2022 Career Guide Free Tutorials Go to Your University Placement Preparation 
0 like 0 dislike
in Tutorial & Interview questions by Goeduhub's Expert (9.3k points)
Inserting a node at the beginning of a singly linked list

1 Answer

0 like 0 dislike
by Goeduhub's Expert (9.3k points)
Best answer

The code below will prompt for numbers and continue to add them to the beginning of a linked list.

/* This program will demonstrate inserting a node at the beginning of a linked list */

#include <stdio.h> 

#include <stdlib.h>

struct Node 


int data;  

struct Node* next; 


void insert_node (struct Node **head, int nodeValue); 

void print_list (struct Node *head);

int main(int argc, char *argv[]) 


struct Node* headNode;  headNode = NULL;         /* Initialize our first node pointer to be NULL. */  

size_t listSize, i;  



printf("How many numbers would you like to input?\n"); 


while(1 != scanf("%zu", &listSize));

for (i = 0; i < listSize; i++) 


int numToAdd;    



printf("Enter a number:\n");    

while (1 != scanf("%d", &numToAdd));

insert_node (&headNode, numToAdd);    

printf("Current list after your inserted node: \n");    



return 0; 


void print_list (struct Node *head) 


struct node* currentNode = head;

  /* Iterate through each link. */  

while (currentNode != NULL) 


printf("Value: %d\n", currentNode->data);      

currentNode = currentNode -> next;  


void insert_node (struct Node **head, int nodeValue) 


struct Node *currentNode = malloc(sizeof *currentNode);  

currentNode->data = nodeValue;  

currentNode->next = (*head);

*head = currentNode; }

Explanation for the Insertion of Nodes

In order to understand how we add nodes at the beginning, let's take a look at possible scenarios:

The list is empty, so we need to add a new node. In which case, our memory looks like this where HEAD is a1. pointer to the first node:

| HEAD | --> NULL

The line currentNode->next = *headNode; will assign the value of currentNode->next to be NULL since headNode originally starts out at a value of NULL.

Now, we want to set our head node pointer to point to our current node.

  -----             ------------

|HEAD | --> |CURRENTNODE| --> NULL /* The head node points to the current node */

-----               ------------

This is done with *headNode = currentNode;

The list is already populated; we need to add a new node to the beginning. For the sake of simplicity, let's2. start out with 1 node:

 -----             ----------


-----              ----------

With currentNode->next = *headNode, the data structure looks like this:

 ---------                -----                  --------------------

currentNode -->  HEAD --> POINTER TO FIRST NODE --> NULL 

---------                 -----                  --------------------

Which, obviously needs to be altered since *headNode should point to currentNode.

 ----             -----------            --------------

HEAD -> currentNode -->     NODE       -> NULL 

----               -----------           --------------

This is done with *headNode = currentNode;

Learn & Improve In-Demand Data Skills Online in this Summer With  These High Quality Courses[Recommended by GOEDUHUB]:-

Best Data Science Online Courses[Lists] on:-

Claim your 10 Days FREE Trial for Pluralsight.

Best Data Science Courses on Datacamp
Best Data Science Courses on Coursera
Best Data Science Courses on Udemy
Best Data Science Courses on Pluralsight
Best Data Science Courses & Microdegrees on Udacity
Best Artificial Intelligence[AI] Courses on Coursera
Best Machine Learning[ML] Courses on Coursera
Best Python Programming Courses on Coursera
Best Artificial Intelligence[AI] Courses on Udemy
Best Python Programming Courses on Udemy

 Important Lists:

Important Lists, Exams & Cutoffs Exams after Graduation PSUs


About Us | Contact Us || Terms & Conditions | Privacy Policy ||  Youtube Channel || Telegram Channel © Social::   |  | 


Free Online Directory