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

typedef struct {
  int *keys;
  int size;
  int front;
  int rear;

} cq;

cq *createqueue(int size) {
  cq *q = (cq *)malloc(sizeof(cq));
  q->size = size;
  q->front = -1;
  q->rear = -1;
  q->keys = (int *)malloc(size * sizeof(int));
  return q;
}

bool isFull(cq *q) { return ((q->rear + 1) % q->size == q->front); }
bool isEmpty(cq *q) { return q->front == -1; }

void enqueue(cq *q, int v) {
  if (isFull(q)) {
    printf("is full");
  }
  if (isEmpty(q)) {
    q->front = 0;
    q->rear = 0;
  } else {
    q->rear = (q->rear + 1) % q->size;
  }
  q->keys[q->rear] = v;
}

int dequeue(cq *q) {
  if (isEmpty(q)) {
    printf("Queue is empty! Cannot delete.\n");
    return -1;
  }
  int v = q->keys[q->front];
  if (q->front == q->rear) {
    q->front = q->rear = -1;

  } else {
    q->front = (q->front + 1) % q->size;
  }
  return v;
}

void display(cq *q) {
  if (isEmpty(q)) {
    printf("Queue is empty!\n");
    return;
  }
  int i = q->front;
  while (1) {
    printf("%d", q->keys[i]);
    if (i == q->rear) {
      break;
    }
    i = (i + 1) % q->size;
  }
}
int main() {
  int n;
  printf("Enter size of queue: ");
  scanf("%d", &n);

  cq *q = createqueue(n);

  enqueue(q, 10);
  enqueue(q, 20);
  enqueue(q, 30);
  display(q);

  dequeue(q);
  display(q);

  enqueue(q, 40);
  enqueue(q, 50);
  display(q);

  dequeue(q);
  display(q);

  free(q->keys);
  free(q);

  return 0;
}