Write a c program to insert an element in the beginning at the end at the specified position in a linear linked list?

Answer 1

#include<stdio.h>

#include<stdlib.h>

typedef struct Node

{

int data;

struct Node *next;

}node;

void insert(node *pointer, int data)

{

/* Iterate through the list till we encounter the last node.*/

while(pointer->next!=NULL)

{

pointer = pointer -> next;

}

/* Allocate memory for the new node and put data in it.*/

pointer->next = (node *)malloc(sizeof(node));

pointer = pointer->next;

pointer->data = data;

pointer->next = NULL;

}

int find(node *pointer, int key)

{

pointer = pointer -> next; //First node is dummy node.

/* Iterate through the entire linked list and search for the key. */

while(pointer!=NULL)

{

if(pointer->data == key) //key is found.

{

return 1;

}

pointer = pointer -> next;//Search in the next node.

}

/*Key is not found */

return 0;

}

void delete(node *pointer, int data)

{

/* Go to the node for which the node next to it has to be deleted */

while(pointer->next!=NULL && (pointer->next)->data != data)

{

pointer = pointer -> next;

}

if(pointer->next==NULL)

{

printf("Element %d is not present in the list\n",data);

return;

}

/* Now pointer points to a node and the node next to it has to be removed */

node *temp;

temp = pointer -> next;

/*temp points to the node which has to be removed*/

pointer->next = temp->next;

/*We removed the node which is next to the pointer (which is also temp) */

free(temp);

/* Beacuse we deleted the node, we no longer require the memory used for it .

free() will deallocate the memory.

*/

return;

}

void print(node *pointer)

{

if(pointer==NULL)

{

return;

}

printf("%d ",pointer->data);

print(pointer->next);

}

int main()

{

/* start always points to the first node of the linked list.

temp is used to point to the last node of the linked list.*/

node *start,*temp;

start = (node *)malloc(sizeof(node));

temp = start;

temp -> next = NULL;

/* Here in this code, we take the first node as a dummy node.

The first node does not contain data, but it used because to avoid handling special cases

in insert and delete functions.

*/

printf("1. Insert\n");

printf("2. Delete\n");

printf("3. Print\n");

printf("4. Find\n");

while(1)

{

int query;

scanf("%d",&query);

if(query==1)

{

int data;

scanf("%d",&data);

insert(start,data);

}

else if(query==2)

{

int data;

scanf("%d",&data);

delete(start,data);

}

else if(query==3)

{

printf("The list is ");

print(start->next);

printf("\n");

}

else if(query==4)

{

int data;

scanf("%d",&data);

int status = find(start,data);

if(status)

{

printf("Element Found\n");

}

else

{

printf("Element Not Found\n");

}

}

}

}