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/*
* This file is part of the MicroPython project, http://micropython.org/
*
* The MIT License (MIT)
*
* Copyright (c) 2020 Damien P. George
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
#include "py/pairheap.h"
// The mp_pairheap_t.next pointer can take one of the following values:
// - NULL: the node is the top of the heap
// - LSB set: the node is the last of the children and points to its parent node
// - other: the node is a child and not the last child
// The macros below help manage this pointer.
#define NEXT_MAKE_RIGHTMOST_PARENT(parent) ((void *)((uintptr_t)(parent) | 1))
#define NEXT_IS_RIGHTMOST_PARENT(next) ((uintptr_t)(next) & 1)
#define NEXT_GET_RIGHTMOST_PARENT(next) ((void *)((uintptr_t)(next) & ~1))
// O(1), stable
mp_pairheap_t *mp_pairheap_meld(mp_pairheap_lt_t lt, mp_pairheap_t *heap1, mp_pairheap_t *heap2) {
if (heap1 == NULL) {
return heap2;
}
if (heap2 == NULL) {
return heap1;
}
if (lt(heap1, heap2)) {
if (heap1->child == NULL) {
heap1->child = heap2;
} else {
heap1->child_last->next = heap2;
}
heap1->child_last = heap2;
heap2->next = NEXT_MAKE_RIGHTMOST_PARENT(heap1);
return heap1;
} else {
heap1->next = heap2->child;
heap2->child = heap1;
if (heap1->next == NULL) {
heap2->child_last = heap1;
heap1->next = NEXT_MAKE_RIGHTMOST_PARENT(heap2);
}
return heap2;
}
}
// amortised O(log N), stable
mp_pairheap_t *mp_pairheap_pairing(mp_pairheap_lt_t lt, mp_pairheap_t *child) {
if (child == NULL) {
return NULL;
}
mp_pairheap_t *heap = NULL;
while (!NEXT_IS_RIGHTMOST_PARENT(child)) {
mp_pairheap_t *n1 = child;
child = child->next;
n1->next = NULL;
if (!NEXT_IS_RIGHTMOST_PARENT(child)) {
mp_pairheap_t *n2 = child;
child = child->next;
n2->next = NULL;
n1 = mp_pairheap_meld(lt, n1, n2);
}
heap = mp_pairheap_meld(lt, heap, n1);
}
heap->next = NULL;
return heap;
}
// amortised O(log N), stable
mp_pairheap_t *mp_pairheap_delete(mp_pairheap_lt_t lt, mp_pairheap_t *heap, mp_pairheap_t *node) {
// Simple case of the top being the node to delete
if (node == heap) {
mp_pairheap_t *child = heap->child;
node->child = NULL;
return mp_pairheap_pairing(lt, child);
}
// Case where node is not in the heap
if (node->next == NULL) {
return heap;
}
// Find parent of node
mp_pairheap_t *parent = node;
while (!NEXT_IS_RIGHTMOST_PARENT(parent->next)) {
parent = parent->next;
}
parent = NEXT_GET_RIGHTMOST_PARENT(parent->next);
// Replace node with pairing of its children
mp_pairheap_t *next;
if (node == parent->child && node->child == NULL) {
if (NEXT_IS_RIGHTMOST_PARENT(node->next)) {
parent->child = NULL;
} else {
parent->child = node->next;
}
node->next = NULL;
return heap;
} else if (node == parent->child) {
mp_pairheap_t *child = node->child;
next = node->next;
node->child = NULL;
node->next = NULL;
node = mp_pairheap_pairing(lt, child);
parent->child = node;
} else {
mp_pairheap_t *n = parent->child;
while (node != n->next) {
n = n->next;
}
mp_pairheap_t *child = node->child;
next = node->next;
node->child = NULL;
node->next = NULL;
node = mp_pairheap_pairing(lt, child);
if (node == NULL) {
node = n;
} else {
n->next = node;
}
}
node->next = next;
if (NEXT_IS_RIGHTMOST_PARENT(next)) {
parent->child_last = node;
}
return heap;
}
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