/* -*- mode: c -*-
 * $Id$
 * http://www.bagley.org/~doug/shootout/
 */

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

#define SIZE 100
#define inline static

/* a simple Double Linked List
   the head node is special, it's val is length of list */
typedef struct DLL {
  int val;
  struct DLL *next;   /* points to next or head (if at tail) */
  struct DLL *prev;   /* points to prev or tail (if at head) */
} DLL;

inline int list_length(DLL *head) { return(head->val); }
inline int list_empty(DLL *head) { return(list_length(head) == 0); }
inline DLL *list_first(DLL *head) { return(head->next); }
inline DLL *list_last(DLL *head) { return(head->prev); }

void list_push_tail(DLL *head, DLL *item) {
  DLL *tail = head->prev;
  tail->next = item;
  item->next = head;
  head->prev = item;
  item->prev = tail;
  head->val++;
}

DLL *list_pop_tail(DLL *head) {
  DLL *prev, *tail;
  if (list_empty(head)) return(NULL);
  tail = head->prev;
  prev = tail->prev;
  prev->next = head;
  head->prev = prev;
  head->val--;
  return(tail);
}

void list_push_head(DLL *head, DLL *item) {
  DLL *next = head->next;
  head->next = item;
  next->prev = item;
  item->next = next;
  item->prev = head;
  head->val++;
}

DLL *list_pop_head(DLL *head) {
  DLL *next;
  if (list_empty(head)) return(NULL);
  next = head->next;
  head->next = next->next;
  next->next->prev = head;
  head->val--;
  return(next);
}

int list_equal(DLL *x, DLL *y) {
  DLL *xp, *yp;
  /* first val's checked will be list lengths */
  for (xp=x, yp=y; xp->next != x; xp=xp->next, yp=yp->next) {
    if (xp->val != yp->val) return(0);
  }
  if (xp->val != yp->val) return(0);
  return(yp->next == y);
}

void list_print(char *msg, DLL *x) {
  DLL *xp, *first = x->next;
  int i = 0;
  puts(msg);
  printf("length: %d\n", list_length(x));
  for (xp=x->next; xp->next != first; xp=xp->next) {
    printf("i:%3d  v:%3d  n:%3d  p:%3d\n", ++i,
           xp->val, xp->next->val, xp->prev->val);
  }
  printf("[last entry points to list head]\n");
  printf("[val of next of tail is:  %d]\n", xp->next->val);
}

DLL *list_new() {
  DLL *l = (DLL *)malloc(sizeof(DLL));
  l->next = l;
  l->prev = l;
  l->val = 0;
  return(l);
}

/* inclusive sequence 'from' <-> 'to' */
DLL *list_sequence(int from, int to) {
  int size, tmp, i, j;
  DLL *l;
  if (from > to) {
    tmp = from; from = to; to = tmp;
  }
  size = to - from + 1;
  l = (DLL *)malloc((size+1) * sizeof(DLL));
  from--;
  for (i=0, j=1; i<size; ++i, ++j) {
    l[i].next = &l[i+1];
    l[j].prev = &l[j-1];
    l[i].val = from++;
  }
  l[0].prev = &l[size];
  l[size].next = &l[0];
  l[size].prev = &l[size-1];
  l[size].val = from;
  l[0].val = size;
  return(l);
}
DLL *list_copy(DLL *x) {
  int i, j, size = list_length(x);
  DLL *xp, *l = (DLL *)malloc((size+1) * sizeof(DLL));
  for (i=0, j=1, xp=x; i<size; i++, j++, xp=xp->next) {
    l[i].next = &l[j];
    l[j].prev = &l[i];
    l[i].val = xp->val;
  }
  l[0].prev = &l[size];
  l[size].next = &l[0];
  l[size].val = list_last(x)->val;
  return(l);
}

void list_reverse (DLL *head) {
  DLL *tmp, *p = head;
  do {
    tmp = p->next;
    p->next = p->prev;
    p->prev = tmp;
    p = tmp;
  } while (p != head);
}

int test_lists() {
  int len = 0;
  /* create a list of integers (li1) from 1 to SIZE */
  DLL *li1 = list_sequence(1, SIZE);
  /* copy the list to li2*/
  DLL *li2 = list_copy(li1);
  /* remove each individual item from left side of li2 and
     append to right side of li3 (preserving order) */
  DLL *li3 = list_new();
  /* compare li2 and li1 for equality */
  if (!list_equal(li2, li1)) {
    printf("li2 and li1 are not equal\n");
    exit(1);
  }
  while (!list_empty(li2)) {
    list_push_tail(li3, list_pop_head(li2));
  }
  /* li2 must now be empty */
  if (!list_empty(li2)) {
    printf("li2 should be empty now\n");
    exit(1);
  }
  /* remove each individual item from right side of li3 and
     append to right side of li2 (reversing list) */
  while (!list_empty(li3)) {
    list_push_tail(li2, list_pop_tail(li3));
  }
  /* li3 must now be empty */
  if (!list_empty(li3)) {
    printf("li3 should be empty now\n");
    exit(1);
  }
  /* reverse li1 in place */
  list_reverse(li1);
  /* check that li1's first item is now SIZE */
  if (list_first(li1)->val != SIZE) {
    printf("li1 first value wrong, wanted %d, got %d\n",
           SIZE, list_first(li1)->val);
    exit(1);
  }
  /* check that li1's last item is now 1 */
  if (list_last(li1)->val != 1) {
    printf("last value wrong, wanted %d, got %d\n",
           SIZE, list_last(li1)->val);
    exit(1);
  }
  /* check that li2's first item is now SIZE */
  if (list_first(li2)->val != SIZE) {
    printf("li2 first value wrong, wanted %d, got %d\n",
           SIZE, list_first(li2)->val);
    exit(1);
  }
  /* check that li2's last item is now 1 */
  if (list_last(li2)->val != 1) {
    printf("last value wrong, wanted %d, got %d\n",
           SIZE, list_last(li2)->val);
    exit(1);
  }
  /* check that li1's length is still SIZE */
  if (list_length(li1) != SIZE) {
    printf("li1 size wrong, wanted %d, got %d\n",
           SIZE, list_length(li1));
    exit(1);
  }
  /* compare li1 and li2 for equality */
  if (!list_equal(li1, li2)) {
    printf("li1 and li2 are not equal\n");
    exit(1);
  }
  len = list_length(li1);
  free(li1);
  free(li2);
  free(li3);
  /* return the length of the list */
  return(len);
}

int main(int argc, char *argv[]) {
#ifdef SMALL_PROBLEM_SIZE
#define LENGTH 300000
#else
#define LENGTH 3000000
#endif
  int n = ((argc == 2) ? atoi(argv[1]) : LENGTH);
  int result = 0;
  while(n--) result = test_lists();
  printf("%d\n", result);
  return 0;
}