Data Structure - Queue Implentation in C
Queue Algorithm
enqueue/insert element to the queue
procedure enqueue(data)
if queue is full
return overflow
endif
rear ← rear + 1
queue[rear] ← data
return true
end procedure
dequeue/delete element from the queue
procedure dequeue
if queue is empty
return underflow
end if
data = queue[front]
front ← front + 1
return true
end procedure
Source Code of Queue implementation in C using Array
#include <stdio.h>
#include <stdlib.h>
#define MAX 50
void enqueue();
void dequeue();
void display();
int queue_array[MAX];
int rear = -1;
int front = -1;
int main()
{
int choice;
while (1)
{
printf("\n1.Enqueue/Insert element to queue \n");
printf("\n2.Dequeue/Delete element from queue \n");
printf("\n3.Display all elements of queue \n");
printf("\n4.Quit \n");
printf("\nEnter your choice : ");
scanf("%d", &choice);
switch (choice)
{
case 1:
enqueue();
break;
case 2:
dequeue();
break;
case 3:
display();
break;
case 4:
exit(1);
default:
printf("Wrong choice \n");
}
}
}
void enqueue()
{
int data;
if (rear == MAX - 1)
printf("Queue Overflow \n");
else
{
if (front == -1)
front = 0;
printf("Inset the element in queue : ");
scanf("%d", &data);
rear = rear + 1;
queue_array[rear] = data;
}
}
void dequeue()
{
if (front == -1 || front > rear)
{
printf("Queue Underflow \n");
return;
}
else
{
printf("Element dequeue from queue is : %d\n", queue_array[front]);
front = front + 1;
}
}
void display()
{
int i;
if (front == -1)
printf("Queue is empty \n");
else
{
printf("Queue is : \n");
for (i = front; i <= rear; i++)
printf("%d ", queue_array[i]);
printf("\n");
}
}
Source Code of Queue implementation in C using Link List
#include<stdio.h>
#include<stdlib.h>
struct Queue //structure is declared
{
struct Queue *next; //self referensing structure
int item; //initailizing item in the structure
};
struct Queue *front; //a pointer front is declared in structure
struct Queue *rear; //a pointer rear is declared in structure
void addq(int); //addq function is declared
int delq(); //delq function id declared
void main()
{
int ch, item, val; //variables are declared
while(1)
{
printf("\nEnter 1 to add element in the Queue");
printf("\nEnter 2 to delete element from the Queue");
printf("\nEnter 3 to exit from program");
printf("\nEnter your choice::");
scanf("%d",&ch);
switch(ch)
{
case 1: printf("\nEnter the item in the list::");
scanf("%d", &item);
addq(item);
break;
case 2: val=delq() ;
printf("\nThe deleted element is %d=",val);
break ;
case 3: exit(1);
default: printf("\nWrong Input") ;
}
}
}
void addq(int item)
{
struct Queue *temp; //a pointer temp is declared within the structure
temp=(struct Queue*)malloc(sizeof(struct Queue));
if(temp==NULL)
{
printf("\nQueue Overflowed");
return;
}
temp->item=item;//the value is entered in the List
temp->next=NULL;
if(rear==NULL)
{
front=temp;
rear=temp;
}
else
{
rear->next=temp;
rear=rear->next; //rear is incremented
}
}
int delq()
{
struct Queue *temp;
int item=0;
if(front==NULL) //checking unerflowed condition
{
printf("\nQueue Underflowed");
return 0;
}
item=front->item;
temp=front;
if(front==NULL) //checking whether front is null or not, if true
{
front=NULL; //front is assign with NULL
rear=NULL;
}
else
{
front=front->next;
free(temp);
}
return item;
}
| Single Link List implementation using C |
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