#include<stdio.h>
#include<stdlib.h>
#define MALLOC(x,size,type) (x=(type*)malloc(size*sizeof(type)))
typedef struct {
int n;
} element;
int front = 0, rear = 0, capacity;
element *queue;
void copy(element *start, element *end, element *newQueue);
void queueFull();
void addq(element item);
element deleteq();
void displayq();
void copy(element *start, element *end, element *newQueue) {
element *j, *i;
i = newQueue;
j = start;
for (; j < end; j++, i++) {
*i = *j;
}
}
void queueFull() {
element *newQueue;
MALLOC(newQueue, capacity * 2, element);
int start = (front + 1) % capacity;
if (start < 2)
copy(queue + start, queue + start + capacity - 1, newQueue);
else {
copy(queue + start, queue + capacity, newQueue);
copy(queue, queue + rear + 1, newQueue + capacity - start);
}
front = 2 * capacity - 1;
rear = capacity - 1;
capacity *= 2;
free(queue);
queue = newQueue;
}
void addq(element item) {
rear = (rear + 1) % capacity;
if (front == rear)
queueFull();
queue[rear] = item;
}
element deleteq() {
element item;
if (front == rear) {
item.n = -1;
return item;
}
front = (front + 1) % capacity;
return queue[front];
}
void displayq() {
int i;
if (front == rear) {
printf("Queue Empty\n");
return;
}
for (i = (front + 1) % capacity; i != rear; i = (i + 1) % capacity)
printf("%d\t", queue[i].n);
printf("%d", queue[i].n);
printf("\n");
}
int main() {
int choice;
element item;
printf("Enter initial size\n");
scanf("%d", &capacity);
MALLOC(queue, capacity, element);
while (1) {
printf("1. Add\n2. Delete\n3. Display\n");
scanf("%d", &choice);
switch (choice) {
case 1:
printf("Enter item to add\n");
scanf("%d", &item.n);
addq(item);
break;
case 2:
item = deleteq();
if (item.n == -1)
printf("Queue Empty\n");
else
printf("Item deleted: %d\n", item.n);
break;
case 3:
displayq();
break;
}
}
return 0;
}