Data structure is collection of data organized in a structured way. It is divided into two types as explained below −
Linear data structure − Data is organized in a linear fashion. For example, arrays, structures, stacks, queues, linked lists.
Nonlinear data structure − Data is organized in a hierarchical way. For example, Trees, graphs, sets, tables.
Queue
It is a linear data structure, where the insertion is done at rear end and the deletion is done at the front end.
The order of queue is FIFO – First In First Out
Operations
- Insert – Inserting an element into a queue.
- Delete – Deleting an element from the queue.
Conditions
Queue over flow − Trying to insert an element into a full queue.
Queue under flow − Trying to delete an element from an empty queue.
Algorithms
Given below is an algorithm for insertion ( ) −
- Check for queue overflow.
if (r==n)
printf ("Queue overflow")- Otherwise, insert an element in to the queue.
q[r] = item r++
Program
Following is the C program for inserting the elements in queue −
#include <stdio.h>
#define MAX 50
void insert();
int array[MAX];
int rear = - 1;
int front = - 1;
main(){
int add_item;
int choice;
while (1){
printf("1.Insert element to queue \n");
printf("2.Display elements of queue \n");
printf("3.Quit \n");
printf("Enter your choice : ");
scanf("%d", &choice);
switch (choice){
case 1:
insert();
break;
case 2:
display();
break;
case 3:
exit(1);
default:
printf("Wrong choice \n");
}
}
}
void insert(){
int add_item;
if (rear == MAX - 1)
printf("Queue Overflow \n");
else{
if (front == - 1)
/*If queue is initially empty */
front = 0;
printf("Inset the element in queue : ");
scanf("%d", &add_item);
rear = rear + 1;
array[rear] = add_item;
}
}
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 ", array[i]);
printf("\n");
}
}Output
When the above program is executed, it produces the following result −
1.Insert element to queue 2.Display elements of queue 3.Quit Enter your choice: 1 Inset the element in queue: 34 1.Insert element to queue 2.Display elements of queue 3.Quit Enter your choice: 1 Inset the element in queue: 24 1.Insert element to queue 2.Display elements of queue 3.Quit Enter your choice: 2 Queue is: 34 24 1.Insert element to queue 2.Display elements of queue 3.Quit Enter your choice: 3