Question

Breadth First Search algorithm, process scheduling, graph theory, and congestion handling in networks are some applications of queues. The two core operations in queues include enqueue () for insertions on one end, and dequeue () for deletions from the other end, size() returns the size of the queue, front() returns the first element in the queue, empty() determines if the queue is empty. Considering the lines give below, write a c program that implements enqueue and dequeue operations and print the resulting queue items after the specified operations below int que [N]: que.enqueue (12): que.enqueue (3): que-enqueue (4): que.dequeue que(): que.enqueue (2 3): que.enqueue (4): que.enqueue (4): que.dequeue (): que.dequeue (): q.enqueue (3): q.enqueue (2 3): que.dequeue (): q.enqueue (3);

Answer 1

#include <stdio.h>
#define MAX 100

//you can declare the basic variable like array, front, rear etc. even local
//but in that case you have to pass all the detail to every calling function
//so to make the program simple i am declaring different data global so that you
//can only focus on implementation

//below variable will be needed for queue implementation
int que[100]; //you can declare array of any size according to your need
int rear = - 1; //a variable which will point to rear element of queue and it will be -1 if queue is empty
int front = - 1; //a variable which will point to front element of queue and it will be -1 if queue is empty

// function definition are after main
main()
{
//que.enqueue() is a c++ style and you asked for c code
//so below code will serve the same purpose
enqueue(12);
enqueue(3);
enqueue(4);
deque();
enqueue(23);
enqueue(4);
enqueue(4);
deque();
deque();
enqueue(3);
enqueue(23);
deque();
enqueue(3);

//now lets display the content of our queue after above operation
display();
}

//below is the function for enqueue operation
void enqueue(int value)
{
if (rear == MAX - 1) //i.e if array to hold element is full then it is the case of overflow
printf("Queue Overflow \n"); //and do nothing
else
{
if (front == - 1)
/*If queue is initially empty */
front = 0; //then we have to set front to 0 as initially it was -1 which show that queue was empty
rear = rear + 1; //making room for inserting new element
que[rear] = value; //inserting element at end/rear
printf("Element inserted in queue is : %d\n", que[rear]);
}
}

void deque()
{
if (front == - 1 || front > rear) //this must be checked whether there is element to delete or not
{
printf("Queue Underflow \n");
return ;
}
else
{
printf("Element deleted from queue is : %d\n", que[front]);
front = front + 1; //since element at front is deleted hence point to next available element in queue
}
}

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 ", que[i]);
printf("\n");
}
}

//sample output

null