/* http://www.cs.nyu.edu/courses/summer07/G22.2110-001/hw05-c-example.txt
 * Rename this file into 'lists.c'.
 * WARNING: This code intentionally contains a bug for education purposes!
 */
#include <assert.h>
#include <stdio.h>
#include <stdlib.h>

struct ListCell {
  int data;
  struct ListCell* next;
};

struct List {
  struct ListCell* head;
};

struct List* listCreate() {
  struct List* result = (struct List*)malloc(sizeof(struct List));
  result->head = NULL;
  return result;
}

void listDestroy(struct List* list) {
  struct ListCell* i = list->head;
  while (NULL != i) {
    struct ListCell* c = i;
    i = i->next;
    free(c);
  }
  free(list);
};

void listEnqueue(struct List* list, int data) {
  struct ListCell* c = (struct ListCell*)malloc(sizeof(struct ListCell));
  c->data = data;
  c->next = list->head;
  list->head = c;
};

int listDequeue(struct List* list) {
  struct ListCell *h = NULL, *i = list->head;
  assert(NULL != i);
  while (NULL != i->next) {
    h = i;
    i = i->next;
  }
  int result = i->data;
  free(i);
  if (NULL != h)
    h->next = NULL;
  return result;
}

int main(int argc, char** argv) {
  struct List* l = listCreate();
  listEnqueue(l, 3);
  listEnqueue(l, 5);
  printf("%d\n", listDequeue(l));
  printf("%d\n", listDequeue(l));
  listDestroy(l);
  return 0;
}