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

typedef struct Employee employee;
struct Employee {
  int eid;
  struct Employee *next;
  struct Employee *prev;
};

typedef struct Employees employees;
struct Employees {
  uint len;
  struct Employee *head;
  struct Employee *tail;
};

employees *init() {
  employees *list = malloc(sizeof(employees));
  list->len = 0;
  list->head = NULL;
  list->tail = NULL;

  return list;
}

void insert(employees *list, uint eid) {
  employee *new = malloc(sizeof(employee));
  new->eid = eid;
  new->prev = NULL;
  new->next = list->head;

  if (list->head)
    list->head->prev = new;
  else
    list->tail = new;

  list->head = new;
  list->len++;
}

void delete (employees *list) {
  employee *prev = list->tail->prev;

  free(list->tail);

  if (prev) {
    prev->next = NULL;
    if (prev->prev == NULL)
      list->head = prev;
  }

  list->tail = prev;
  list->len--;
}

int main() {
  employees *list = init();
  insert(list, 4);
  insert(list, 20);
  insert(list, 300);
  insert(list, 44);
  delete (list);

  employee *cur = list->head;
  while (cur != NULL) {
    printf("%d ", cur->eid);
    cur = cur->next;
  }

  // free
  while (list->tail != NULL)
    delete (list);

  free(list);
}