Enqueue/Dequeue

int front,back;

front = back = -1;

void Enqueue(int n){
    arr[++back] = n;

    if(front == -1)front++;
}

int Dequeue(){
    if(front == -1){
        printf("Queue is empty");
        return -1;
    }

    int x = arr[front];
    if(front == back){
        front = back = -1;
    }

    front++;

    return x;

}