Global Circular Queue Implementation in C

circular_q_global.c

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

static int front = 0;
static int rear = 0;
static int capacity = 2;

static int* q;

void enq(int element) {
    if (((rear+1)%capacity) == front) { // q is full, double the capacity
        int* newq = (int*)malloc(sizeof(int)*2*capacity);
        int newrear = 0, newfront = 0, start = (front + 1) % capacity;
        for (; start != rear; start = (start + 1) % capacity) { // you can write this for loop too, init step is not present
            newq[++newrear] = q[start];
        }
        newq[++newrear] = q[start];
        q = newq;
        capacity *= 2;
        front = newfront;
        rear = newrear;
    }
    
    rear = (rear + 1) % capacity;
    q[rear] = element;
}

int deq() {
    if (front == rear) { // q is empty
        printf("\nQ is empty");
        return -1;
    }
    
    front = (front + 1) % capacity;
    return q[front];
}


int main() {
    q = (int*)malloc(sizeof(int)*capacity);
    
    for (int i = 0; i < 10; ++i) {
        printf("\nENQ(%d)", i);
        enq(i);
    }
    
    for (int j = 0; j < 12; ++j) {
        int dequeuedElement = deq();
        if (dequeuedElement != -1) { // q is not empty
            printf("\n%d is dequeued", dequeuedElement);            
        }
    }

    return 0;
}