Notes

#include <stdio.h>
#include <stdlib.h>

#define MAXELEMENTS 5
#define TRUE 1
#define FALSE 0

struct queue {
int items[MAXELEMENTS];
int insertValues[MAXELEMENTS];
int deleteValues[MAXELEMENTS];
int front, rear;
int insertPoint, deletePoint;
};

void cqinsert(struct queue *, int);
int cqdelete(struct queue *);
int empty(struct queue *);

int main(void) {
char operation;
int x;
struct queue q;
q.front = q.rear = MAXELEMENTS - 1;
q.insertPoint = q.deletePoint = -1;

do {
printf("Insert Operation type I D or E: ");
scanf(" %c", &operation);

switch (operation) {
case 'I':
printf("Insert an element: ");
scanf("%d", &x);
cqinsert(&q, x);
break;
case 'D':
x = cqdelete(&q);
printf("%d is deleted from location %dn", x, q.deletePoint);
break;
}
} while (operation != 'E');

return 0;
}

int empty(struct queue *pq) {
return (pq->front == pq->rear) ? TRUE : FALSE;
}

void cqinsert(struct queue *pq, int x) {
if (pq->rear == MAXELEMENTS - 1)
pq->rear = 0;
else
(pq->rear)++;

if (pq->rear == pq->front) {
printf("Queue overflow");
getchar();
getchar();
exit(1);
}

printf("%d is inserted at location %dn", x, pq->rear);
pq->items[pq->rear] = x;
pq->insertValues[pq->rear] = x;
pq->insertPoint = pq->rear;
}

int cqdelete(struct queue *pq) {
if (empty(pq)) {
printf("Queue underflow");
exit(1);
}

if (pq->front == MAXELEMENTS - 1)
pq->front = 0;
else
(pq->front)++;

pq->deleteValues[pq->front] = pq->items[pq->front];
pq->deletePoint = pq->front;

return pq->items[pq->front];
}