Explain queue by using linked list in C language

CServer Side ProgrammingProgramming

Queue overflow and Queue under flow can be avoided by using linked list.

Operations carried out under queue with the help of linked lists in C programming language are as follows −

  • Insert
  • Delete

Insertion

The syntax is as follows −

Syntax

&item :
Newnode = (node*) mallac (sizeof (node));
newnode ->data = item;
newnode ->link = NULL;
if ((front = = NULL) || (rear = = NULL)){
   front= newnode;
   rear = newnode;
}else{
   Rear->link = newnode;
   rear = newnode;
}

Deletion

The syntax is as follows −

Syntax

if ((front= = NULL))
printf("Deletion is not possible, Queue is empty");
else{
   temp = front;
   front = front ->link;
   free (temp);
}

Display

The syntax is as follows −

Syntax

while (front! = NULL){
   printf("%d", front ->data);
   front = front->link;
}

Program

Following is the C program for queue by using linked lists −

#include <stdio.h>
#include <stdlib.h>
struct node{
   int info;
   struct node *ptr;
}*front,*rear,*temp,*front1;
int frontelement();
void enq(int data);
void deq();
void display();
void create();
int count = 0;
void main(){
   int no, ch, e;
   printf("
1 - Enqueue");    printf("
2 - Dequeue");    printf("
3 - Display");    printf("
4 - Exit");    printf("
5-front");    create();    while (1){       printf("
Enter choice : ");       scanf("%d", &ch);       switch (ch){          case 1:             printf("Enter data : ");          scanf("%d", &no);          enq(no);          break;          case 2:             deq();          break;          case 3:             display();          break;          case 4:             exit(0);          break;          case 5:             e = frontelement();          if (e != 0)             printf("Front element : %d", e);          else             printf("
No front element in Queue");          break;          default:          printf("Wrong choice, Try again ");          break;       }    } } void enq(int data){    if (rear == NULL){       rear = (struct node *)malloc(1*sizeof(struct node));       rear->ptr = NULL;       rear->info = data;       front = rear;    }else{       temp=(struct node *)malloc(1*sizeof(struct node));       rear->ptr = temp;       temp->info = data;       temp->ptr = NULL;       rear = temp;    }    count++; } void display(){    front1 = front;    if ((front1 == NULL) && (rear == NULL)){       printf("Queue is empty");       return;    }    while (front1 != rear){       printf("%d ", front1->info);       front1 = front1->ptr;    }    if (front1 == rear)       printf("%d", front1->info);    }    void deq(){       front1 = front;       if (front1 == NULL){          printf("
Error");          return;       }       else       if (front1->ptr != NULL){          front1 = front1->ptr;          printf("
Dequeued value : %d", front->info);          free(front);          front = front1;       }else{          printf("
Dequeued value : %d", front->info);          free(front);          front = NULL;       rear = NULL;    }    count--; } int frontelement(){    if ((front != NULL) && (rear != NULL))       return(front->info);    else       return 0; }

Output

When the above program is executed, it produces the following result −

1 - Enque
2 - Deque
3 – Display
4 - Exit
5 - Front element
Enter choice: 1
Enter data: 14
Enter choice: 1
Enter data: 85
Enter choice: 1
Enter data: 38
Enter choice: 5
Front element: 14
Enter choice: 3
14 85 38
Enter choice: 2
Dequed value: 14
Enter choice: 3
Enter choice: 4
raja
Updated on 26-Mar-2021 06:52:11

Advertisements