101 lines
4.0 KiB
C
101 lines
4.0 KiB
C
/*
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* This file is part of the MicroPython project, http://micropython.org/
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*
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* The MIT License (MIT)
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*
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* Copyright (c) 2020 Damien P. George
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*
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* Permission is hereby granted, free of charge, to any person obtaining a copy
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* of this software and associated documentation files (the "Software"), to deal
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* in the Software without restriction, including without limitation the rights
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* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
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* copies of the Software, and to permit persons to whom the Software is
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* furnished to do so, subject to the following conditions:
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*
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* The above copyright notice and this permission notice shall be included in
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* all copies or substantial portions of the Software.
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*
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* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
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* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
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* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
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* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
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* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
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* THE SOFTWARE.
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*/
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#ifndef MICROPY_INCLUDED_PY_PAIRHEAP_H
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#define MICROPY_INCLUDED_PY_PAIRHEAP_H
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// This is an implementation of a pairing heap. It is stable and has deletion
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// support. Only the less-than operation needs to be defined on elements.
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//
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// See original paper for details:
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// Michael L. Fredman, Robert Sedjewick, Daniel D. Sleator, and Robert E. Tarjan.
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// The Pairing Heap: A New Form of Self-Adjusting Heap.
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// Algorithmica 1:111-129, 1986.
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// https://www.cs.cmu.edu/~sleator/papers/pairing-heaps.pdf
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#include <assert.h>
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#include "py/obj.h"
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// This struct forms the nodes of the heap and is intended to be extended, by
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// placing it first in another struct, to include additional information for the
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// element stored in the heap. It includes "base" so it can be a MicroPython
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// object allocated on the heap and the GC can automatically trace all nodes by
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// following the tree structure.
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typedef struct _mp_pairheap_t {
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mp_obj_base_t base;
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struct _mp_pairheap_t *child;
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struct _mp_pairheap_t *child_last;
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struct _mp_pairheap_t *next;
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} mp_pairheap_t;
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// This is the function for the less-than operation on nodes/elements.
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typedef int (*mp_pairheap_lt_t)(mp_pairheap_t *, mp_pairheap_t *);
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// Core functions.
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mp_pairheap_t *mp_pairheap_meld(mp_pairheap_lt_t lt, mp_pairheap_t *heap1, mp_pairheap_t *heap2);
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mp_pairheap_t *mp_pairheap_pairing(mp_pairheap_lt_t lt, mp_pairheap_t *child);
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mp_pairheap_t *mp_pairheap_delete(mp_pairheap_lt_t lt, mp_pairheap_t *heap, mp_pairheap_t *node);
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// Create a new heap.
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static inline mp_pairheap_t *mp_pairheap_new(mp_pairheap_lt_t lt) {
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(void)lt;
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return NULL;
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}
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// Initialise a single pairing-heap node so it is ready to push on to a heap.
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static inline void mp_pairheap_init_node(mp_pairheap_lt_t lt, mp_pairheap_t *node) {
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(void)lt;
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node->child = NULL;
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node->next = NULL;
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}
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// Test if the heap is empty.
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static inline bool mp_pairheap_is_empty(mp_pairheap_lt_t lt, mp_pairheap_t *heap) {
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(void)lt;
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return heap == NULL;
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}
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// Peek at the top of the heap. Will return NULL if empty.
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static inline mp_pairheap_t *mp_pairheap_peek(mp_pairheap_lt_t lt, mp_pairheap_t *heap) {
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(void)lt;
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return heap;
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}
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// Push new node onto existing heap. Returns the new heap.
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static inline mp_pairheap_t *mp_pairheap_push(mp_pairheap_lt_t lt, mp_pairheap_t *heap, mp_pairheap_t *node) {
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assert(node->child == NULL && node->next == NULL);
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return mp_pairheap_meld(lt, node, heap); // node is first to be stable
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}
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// Pop the top off the heap, which must not be empty. Returns the new heap.
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static inline mp_pairheap_t *mp_pairheap_pop(mp_pairheap_lt_t lt, mp_pairheap_t *heap) {
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assert(heap->next == NULL);
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mp_pairheap_t *child = heap->child;
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heap->child = NULL;
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return mp_pairheap_pairing(lt, child);
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}
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#endif // MICROPY_INCLUDED_PY_PAIRHEAP_H
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