﻿ C exercises: Insert a new node at the beginning of a Singly Linked List - w3resource

# C Exercises: Insert a new node at the beginning of a Singly Linked List

## C Linked List : Exercise-4 with Solution

Write a program in C to insert a new node at the beginning of a Singly Linked List.

Sample Solution:

C Code:

``````#include <stdio.h>
#include <stdlib.h>

struct node
{
int num;                    //Data of the node
struct node *nextptr;       //Address of the node
}*stnode;

void createNodeList(int n);     //function to create the list
void NodeInsertatBegin(int num);	            //function to insert node at the beginning
void displayList();             //function to display the list

int main()
{
int n,num;
printf("\n\n Linked List : Insert a new node at the beginning of a Singly Linked List:\n");
printf("------------------------------------------------------------------------------\n");
printf(" Input the number of nodes : ");
scanf("%d", &n);
createNodeList(n);
printf("\n Data entered in the list are : \n");
displayList();
printf("\n Input data to insert at the beginning of the list : ");
scanf("%d", &num);
NodeInsertatBegin(num);
printf("\n Data after inserted in the list are : \n");
displayList();

return 0;
}
void createNodeList(int n)
{
struct node *fnNode, *tmp;
int num, i;

stnode = (struct node *)malloc(sizeof(struct node));
if(stnode == NULL) //check whether the stnode is NULL and if so no memory allocation
{
printf(" Memory can not be allocated.");
}
else
{
// reads data for the node through keyboard
printf(" Input data for node 1 : ");
scanf("%d", &num);
stnode-> num = num;
tmp = stnode;

for(i=2; i<=n; i++)
{
fnNode = (struct node *)malloc(sizeof(struct node));

if(fnNode == NULL) //check whether the fnnode is NULL and if so no memory allocation
{
printf(" Memory can not be allocated.");
break;
}
else
{
printf(" Input data for node %d : ", i);
scanf(" %d", &num);
fnNode->num = num;      // links the num field of fnNode with num
fnNode->nextptr = NULL; // links the address field of fnNode with NULL
tmp->nextptr = fnNode; // links previous node i.e. tmp to the fnNode
tmp = tmp->nextptr;
}
}
}
}

void NodeInsertatBegin(int num)
{
struct node *fnNode;
fnNode = (struct node*)malloc(sizeof(struct node));
if(fnNode == NULL)
{
printf(" Memory can not be allocated.");
}
else
{
fnNode->num = num; //Links the data part
stnode = fnNode; //Makes stnode as first node
}
}

void displayList()
{
struct node *tmp;
if(stnode == NULL)
{
printf(" No data found in the list.");
}
else
{
tmp = stnode;
while(tmp != NULL)
{
printf(" Data = %d\n", tmp->num);   // prints the data of current node
tmp = tmp->nextptr;                 // advances the position of current node
}
}
}
```
```

Sample Output:

``` Linked List : Insert a new node at the beginning of a Singly Linked List:
------------------------------------------------------------------------------
Input the number of nodes : 3
Input data for node 1 : 5
Input data for node 2 : 6
Input data for node 3 : 7

Data entered in the list are :
Data = 5
Data = 6
Data = 7

Input data to insert at the beginning of the list : 4

Data after inserted in the list are :
Data = 4
Data = 5
Data = 6
Data = 7
```

Flowchart:

createNodeList() :

NodeInsertatBegin() :

displayList() :

C Programming Code Editor:

```#include <stdio.h>
#include <stdlib.h>

struct node
{
int num;                    //Data of the node
struct node *nextptr;       //Address of the node
}*stnode;

void createNodeList(int n);     //function to create the list
void NodeInsertatBegin(int num);	            //function to insert node at the beginning
void displayList();             //function to display the list

int main()
{
int n,num;
printf("\n\n Linked List : Insert a new node at the beginning of a Singly Linked List:\n");
printf("------------------------------------------------------------------------------\n");
printf(" Input the number of nodes : ");
scanf("%d", &n);
createNodeList(n);
printf("\n Data entered in the list are : \n");
displayList();
printf("\n Input data to insert at the beginning of the list : ");
scanf("%d", &num);
NodeInsertatBegin(num);
printf("\n Data after inserted in the list are : \n");
displayList();

return 0;
}
void createNodeList(int n)
{
struct node *fnNode, *tmp;
int num, i;

stnode = (struct node *)malloc(sizeof(struct node));
if(stnode == NULL) //check whether the stnode is NULL and if so no memory allocation
{
printf(" Memory can not be allocated.");
}
else
{
// reads data for the node through keyboard
printf(" Input data for node 1 : ");
scanf("%d", &num);
stnode-> num = num;
tmp = stnode;

for(i=2; i<=n; i++)
{
fnNode = (struct node *)malloc(sizeof(struct node));

if(fnNode == NULL) //check whether the fnnode is NULL and if so no memory allocation
{
printf(" Memory can not be allocated.");
break;
}
else
{
printf(" Input data for node %d : ", i);
scanf(" %d", &num);
fnNode->num = num;      // links the num field of fnNode with num
fnNode->nextptr = NULL; // links the address field of fnNode with NULL
tmp->nextptr = fnNode; // links previous node i.e. tmp to the fnNode
tmp = tmp->nextptr;
}
}
}
}

void NodeInsertatBegin(int num)
{
struct node *fnNode;
fnNode = (struct node*)malloc(sizeof(struct node));
if(fnNode == NULL)
{
printf(" Memory can not be allocated.");
}
else
{
fnNode->num = num; //Links the data part
stnode = fnNode; //Makes stnode as first node
}
}

void displayList()
{
struct node *tmp;
if(stnode == NULL)
{
printf(" No data found in the list.");
}
else
{
tmp = stnode;
while(tmp != NULL)
{
printf(" Data = %d\n", tmp->num);   // prints the data of current node
tmp = tmp->nextptr;                 // advances the position of current node
}
}
} ```

Improve this sample solution and post your code through Disqus.