Question

in the c programming language.

List *init()

{

   head = ( List * ) malloc( sizeof( List ) );

   if ( head == NULL ) {

      prtError( "Insufficient memory!" );

      return( NULL );

   }

   head->data = -1;

   head->next = NULL;

   tail = head;

   return ( head );

}

/* Insert a new data element d into the list. */

/* Insert at the front of the list, right behind the dummy node. */

/* Return NULL if a new node cannot be created. */

/* Otherwise, return the pointer to the newly created node. */

List *insertFirst( int d )

{

   /***** ADD YOUR CODE HERE *****/

}

/* Insert a new data element d into the list. */

/* Insert at the end of the list. */

/* Return NULL if a new node cannot be created. */

/* Otherwise, return the pointer to the newly created node. */

List *insertLast( int d )

{

   /***** ADD YOUR CODE HERE *****/

}

/* Remove the first element of the list, i.e., the node right behind the dummy node. */

/* Return -1 if the list is empty, i.e., containing only the dummy node, */

/* and display error message "Empty list!" on the standard output. */

/* Otherwise, return the data (integer) of the node to be remove. */

int removeFirst()

{

   /***** ADD YOUR CODE HERE *****/

}

/* Search the list for an element containing integer k. */

/* If found, return the pointer to that element.  Otherwise, return NULL. */

/* If there is more than one element containing k, return the pointer to the first encountered element. */

List *search( int k )

{

   /***** ADD YOUR CODE HERE *****/

}

Answer 1

#include<stdio.h>
#include<stdlib.h>// for using malloc()

// define the structure for node
struct List {

struct List * next ;
int data;
};

struct List * head = NULL ;

struct List *init(){;
head = ( struct List * ) malloc( sizeof( struct List ) );
if ( head == NULL ) {
printf( "Insufficient memory!" );
return( NULL );
}
head->data = -1;

head->next = NULL;
return ( head );

}

/* Insert a new data element d into the list. */

/* Insert at the front of the list, right behind the dummy node. */

/* Return NULL if a new node cannot be created. */

/* Otherwise, return the pointer to the newly created node. */

struct List *insertFirst( int d )
{ //create new node
struct List * newNode = (struct List * ) malloc( sizeof( struct List ) );
// if node cannot be created
if ( newNode == NULL ) {
printf( "Node cannot be created " );
return( NULL );
}
else //attach the newley created node
newNode->data = d ;
head->next = newNode;
newNode->next = NULL;
return head ;
}
/* Insert a new data element d into the list. */

/* Insert at the end of the list. */

/* Return NULL if a new node cannot be created. */

/* Otherwise, return the pointer to the newly created node. */

struct List *insertLast( int d )

{//create a node
struct List * lNode = NULL ;
lNode = ( struct List * ) malloc( sizeof( struct List ) );

if ( lNode == NULL ) {

printf( "Insufficient memory!" );

return( NULL );

}
else // find the current last node
{
struct List * curr = head ;
while(curr->next != NULL)// to reach to the last node
{
curr = curr->next ;
}
// you are currently at the last node
curr->next = lNode ;// attach created node at the last
//assign value to this node
lNode->data = d ;
return head;
}
}
/* Remove the first element of the list, i.e., the node right behind the dummy node. */

/* Return -1 if the list is empty, i.e., containing only the dummy node, */

/* and display error message "Empty list!" on the standard output. */

/* Otherwise, return the data (integer) of the node to be remove. */

int removeFirst(){
if( head== NULL )
printf("Empty list ");
else
{
struct List* list = head ->next ;//list is pointing to right of dummy node
int value = list->data ;
head->next = head->next->next ;
free(list);
return value;
}
}

/* Search the list for an element containing integer k. */

/* If found, return the pointer to that element. Otherwise, return NULL. */

/* If there is more than one element containing k, return the pointer to the first encountered element. */

struct List *search( int k )
{
struct List * list= head ;
while( list != NULL )
{
if( list->data = k)
return list;
}
printf("Element not found in the List ");

return NULL ;
}
// program to print element of linked list
void print_list( struct List * head ){
struct List *parse = head ;
while( parse != NULL )
{
printf( "%d \t " , parse->data);

parse = parse->next ;

}
printf("\n");
}

int main(){

struct List * head = init();
insertFirst(3);
insertLast(4);
printf("current list elements :\n");
print_list(head);
removeFirst(head);
printf("current list elements after calling removeFirst :\n");
print_list(head);
printf("let insert more elements using insertLast:\n");
insertLast(9);
insertLast(5);

print_list(head);}