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/* A Fibonacci heap datatype.

   Copyright 1998, 1999, 2000, 2001 Free Software Foundation, Inc.

   Contributed by Daniel Berlin (dan@cgsoftware.com).

This file is part of GNU CC.

GNU CC is free software; you can redistribute it and/or modify it

under the terms of the GNU General Public License as published by

the Free Software Foundation; either version 2, or (at your option)

any later version.

GNU CC is distributed in the hope that it will be useful, but

WITHOUT ANY WARRANTY; without even the implied warranty of

MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

General Public License for more details.

You should have received a copy of the GNU General Public License

along with GNU CC; see the file COPYING.  If not, write to

the Free Software Foundation, 51 Franklin Street - Fifth Floor,

Boston, MA 02110-1301, USA.  */

#ifdef HAVE_CONFIG_H

#include "config.h"

#endif

#ifdef HAVE_LIMITS_H

#include <limits.h>

#endif

#ifdef HAVE_STDLIB_H

#include <stdlib.h>

#endif

#ifdef HAVE_STRING_H

#include <string.h>

#endif

#include "libiberty.h"

#include "fibheap.h"

#define FIBHEAPKEY_MIN  LONG_MIN

static void fibheap_ins_root (fibheap_t, fibnode_t);

static void fibheap_rem_root (fibheap_t, fibnode_t);

static void fibheap_consolidate (fibheap_t);

static void fibheap_link (fibheap_t, fibnode_t, fibnode_t);

static void fibheap_cut (fibheap_t, fibnode_t, fibnode_t);

static void fibheap_cascading_cut (fibheap_t, fibnode_t);

static fibnode_t fibheap_extr_min_node (fibheap_t);

static int fibheap_compare (fibheap_t, fibnode_t, fibnode_t);

static int fibheap_comp_data (fibheap_t, fibheapkey_t, void *, fibnode_t);

static fibnode_t fibnode_new (void);

static void fibnode_insert_after (fibnode_t, fibnode_t);

#define fibnode_insert_before(a, b) fibnode_insert_after (a->left, b)

static fibnode_t fibnode_remove (fibnode_t);

/* Create a new fibonacci heap.  */

fibheap_t

fibheap_new (void)

{

  return (fibheap_t) xcalloc (1, sizeof (struct fibheap));

}

/* Create a new fibonacci heap node.  */

static fibnode_t

fibnode_new (void)

{

  fibnode_t node;

  node = (fibnode_t) xcalloc (1, sizeof *node);

  node->left = node;

  node->right = node;

  return node;

}

static inline int

fibheap_compare (fibheap_t heap ATTRIBUTE_UNUSED, fibnode_t a, fibnode_t b)

{

  if (a->key < b->key)

    return -1;

  if (a->key > b->key)

    return 1;

  return 0;

}

static inline int

fibheap_comp_data (fibheap_t heap, fibheapkey_t key, void *data, fibnode_t b)

{

  struct fibnode a;

  a.key = key;

  a.data = data;

  return fibheap_compare (heap, &a, b);

}

/* Insert DATA, with priority KEY, into HEAP.  */

fibnode_t

fibheap_insert (fibheap_t heap, fibheapkey_t key, void *data)

{

  fibnode_t node;

  /* Create the new node.  */

  node = fibnode_new ();

  /* Set the node's data.  */

  node->data = data;

  node->key = key;

  /* Insert it into the root list.  */

  fibheap_ins_root (heap, node);

  /* If their was no minimum, or this key is less than the min,

     it's the new min.  */

  if (heap->min == NULL || node->key < heap->min->key)

    heap->min = node;

  heap->nodes++;

  return node;

}

/* Return the data of the minimum node (if we know it).  */

void *

fibheap_min (fibheap_t heap)

{

  /* If there is no min, we can't easily return it.  */

  if (heap->min == NULL)

    return NULL;

  return heap->min->data;

}

/* Return the key of the minimum node (if we know it).  */

fibheapkey_t

fibheap_min_key (fibheap_t heap)

{

  /* If there is no min, we can't easily return it.  */

  if (heap->min == NULL)

    return 0;

  return heap->min->key;

}

/* Union HEAPA and HEAPB into a new heap.  */

fibheap_t

fibheap_union (fibheap_t heapa, fibheap_t heapb)

{

  fibnode_t a_root, b_root, temp;

  /* If one of the heaps is empty, the union is just the other heap.  */

  if ((a_root = heapa->root) == NULL)

    {

      free (heapa);

      return heapb;

    }

  if ((b_root = heapb->root) == NULL)

    {

      free (heapb);

      return heapa;

    }

  /* Merge them to the next nodes on the opposite chain.  */

  a_root->left->right = b_root;

  b_root->left->right = a_root;

  temp = a_root->left;

  a_root->left = b_root->left;

  b_root->left = temp;

  heapa->nodes += heapb->nodes;

  /* And set the new minimum, if it's changed.  */

  if (fibheap_compare (heapa, heapb->min, heapa->min) < 0)

    heapa->min = heapb->min;

  free (heapb);

  return heapa;

}

/* Extract the data of the minimum node from HEAP.  */

void *

fibheap_extract_min (fibheap_t heap)

{

  fibnode_t z;

  void *ret = NULL;

  /* If we don't have a min set, it means we have no nodes.  */

  if (heap->min != NULL)

    {

      /* Otherwise, extract the min node, free the node, and return the

         node's data.  */

      z = fibheap_extr_min_node (heap);

      ret = z->data;

      free (z);

    }

  return ret;

}

/* Replace both the KEY and the DATA associated with NODE.  */

void *

fibheap_replace_key_data (fibheap_t heap, fibnode_t node,

                          fibheapkey_t key, void *data)

{

  void *odata;

  fibheapkey_t okey;

  fibnode_t y;

  /* If we wanted to, we could actually do a real increase by redeleting and

     inserting. However, this would require O (log n) time. So just bail out

     for now.  */

  if (fibheap_comp_data (heap, key, data, node) > 0)

    return NULL;

  odata = node->data;

  okey = node->key;

  node->data = data;

  node->key = key;

  y = node->parent;

  if (okey == key)

    return odata;

  /* These two compares are specifically <= 0 to make sure that in the case

     of equality, a node we replaced the data on, becomes the new min.  This

     is needed so that delete's call to extractmin gets the right node.  */

  if (y != NULL && fibheap_compare (heap, node, y) <= 0)

    {

      fibheap_cut (heap, node, y);

      fibheap_cascading_cut (heap, y);

    }

  if (fibheap_compare (heap, node, heap->min) <= 0)

    heap->min = node;

  return odata;

}

/* Replace the DATA associated with NODE.  */

void *

fibheap_replace_data (fibheap_t heap, fibnode_t node, void *data)

{

  return fibheap_replace_key_data (heap, node, node->key, data);

}

/* Replace the KEY associated with NODE.  */

fibheapkey_t

fibheap_replace_key (fibheap_t heap, fibnode_t node, fibheapkey_t key)

{

  int okey = node->key;

  fibheap_replace_key_data (heap, node, key, node->data);

  return okey;

}

/* Delete NODE from HEAP.  */

void *

fibheap_delete_node (fibheap_t heap, fibnode_t node)

{

  void *ret = node->data;

  /* To perform delete, we just make it the min key, and extract.  */

  fibheap_replace_key (heap, node, FIBHEAPKEY_MIN);

  fibheap_extract_min (heap);

  return ret;

}

/* Delete HEAP.  */

void

fibheap_delete (fibheap_t heap)

{

  while (heap->min != NULL)

    free (fibheap_extr_min_node (heap));

  free (heap);

}

/* Determine if HEAP is empty.  */

int

fibheap_empty (fibheap_t heap)

{

  return heap->nodes == 0;

}

/* Extract the minimum node of the heap.  */

static fibnode_t

fibheap_extr_min_node (fibheap_t heap)

{

  fibnode_t ret = heap->min;

  fibnode_t x, y, orig;

  /* Attach the child list of the minimum node to the root list of the heap.

     If there is no child list, we don't do squat.  */

  for (x = ret->child, orig = NULL; x != orig && x != NULL; x = y)

    {

      if (orig == NULL)

        orig = x;

      y = x->right;

      x->parent = NULL;

      fibheap_ins_root (heap, x);

    }

  /* Remove the old root.  */

  fibheap_rem_root (heap, ret);

  heap->nodes--;

  /* If we are left with no nodes, then the min is NULL.  */

  if (heap->nodes == 0)

    heap->min = NULL;

  else

    {

      /* Otherwise, consolidate to find new minimum, as well as do the reorg

         work that needs to be done.  */

      heap->min = ret->right;

      fibheap_consolidate (heap);

    }

  return ret;

}

/* Insert NODE into the root list of HEAP.  */

static void

fibheap_ins_root (fibheap_t heap, fibnode_t node)

{

  /* If the heap is currently empty, the new node becomes the singleton

     circular root list.  */

  if (heap->root == NULL)

    {

      heap->root = node;

      node->left = node;

      node->right = node;

      return;

    }

  /* Otherwise, insert it in the circular root list between the root

     and it's right node.  */

  fibnode_insert_after (heap->root, node);

}

/* Remove NODE from the rootlist of HEAP.  */

static void

fibheap_rem_root (fibheap_t heap, fibnode_t node)

{

  if (node->left == node)

    heap->root = NULL;

  else

    heap->root = fibnode_remove (node);

}

/* Consolidate the heap.  */

static void

fibheap_consolidate (fibheap_t heap)

{

  fibnode_t a[1 + 8 * sizeof (long)];

  fibnode_t w;

  fibnode_t y;

  fibnode_t x;

  int i;

  int d;

  int D;

  D = 1 + 8 * sizeof (long);

  memset (a, 0, sizeof (fibnode_t) * D);

  while ((w = heap->root) != NULL)

    {

      x = w;

      fibheap_rem_root (heap, w);

      d = x->degree;

      while (a[d] != NULL)

        {

          y = a[d];

          if (fibheap_compare (heap, x, y) > 0)

            {

              fibnode_t temp;

              temp = x;

              x = y;

              y = temp;

            }

          fibheap_link (heap, y, x);

          a[d] = NULL;

          d++;

        }

      a[d] = x;

    }

  heap->min = NULL;

  for (i = 0; i < D; i++)

    if (a[i] != NULL)

      {

        fibheap_ins_root (heap, a[i]);

        if (heap->min == NULL || fibheap_compare (heap, a[i], heap->min) < 0)

          heap->min = a[i];

      }

}

/* Make NODE a child of PARENT.  */

static void

fibheap_link (fibheap_t heap ATTRIBUTE_UNUSED,

              fibnode_t node, fibnode_t parent)

{

  if (parent->child == NULL)

    parent->child = node;

  else

    fibnode_insert_before (parent->child, node);

  node->parent = parent;

  parent->degree++;

  node->mark = 0;

}

/* Remove NODE from PARENT's child list.  */

static void

fibheap_cut (fibheap_t heap, fibnode_t node, fibnode_t parent)

{

  fibnode_remove (node);

  parent->degree--;

  fibheap_ins_root (heap, node);

  node->parent = NULL;

  node->mark = 0;

}

static void

fibheap_cascading_cut (fibheap_t heap, fibnode_t y)

{

  fibnode_t z;

  while ((z = y->parent) != NULL)

    {

      if (y->mark == 0)

        {

          y->mark = 1;

          return;

        }

      else

        {

          fibheap_cut (heap, y, z);

          y = z;

        }

    }

}

static void

fibnode_insert_after (fibnode_t a, fibnode_t b)

{

  if (a == a->right)

    {

      a->right = b;

      a->left = b;

      b->right = a;

      b->left = a;

    }

  else

    {

      b->right = a->right;

      a->right->left = b;

      a->right = b;

      b->left = a;

    }

}

static fibnode_t

fibnode_remove (fibnode_t node)

{

  fibnode_t ret;

  if (node == node->left)

    ret = NULL;

  else

    ret = node->left;

  if (node->parent != NULL && node->parent->child == node)

    node->parent->child = ret;

  node->right->left = node->left;

  node->left->right = node->right;

  node->parent = NULL;

  node->left = node;

  node->right = node;

  return ret;

}