forked from vieter-v/libvieter
193 lines
5.1 KiB
C
193 lines
5.1 KiB
C
#include "vieter_heap_tree.h"
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vieter_heap_node *vieter_heap_node_init() {
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return calloc(1, sizeof(vieter_heap_node));
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}
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void vieter_heap_node_free(vieter_heap_node *node) { free(node); }
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void vieter_heap_tree_free(vieter_heap_node *root) {
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if (root->order == 0) {
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goto end;
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}
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uint64_t size = 1;
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vieter_heap_node **stack =
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malloc(((uint64_t)1 << root->order) * sizeof(vieter_heap_node *));
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stack[0] = root->largest_order;
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vieter_heap_node *node;
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while (size > 0) {
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node = stack[size - 1];
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size--;
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if (node->largest_order != NULL) {
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stack[size] = node->largest_order;
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size++;
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}
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if (node->ptr.next_largest_order != NULL) {
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stack[size] = node->ptr.next_largest_order;
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size++;
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}
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vieter_heap_node_free(node);
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}
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free(stack);
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end:
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vieter_heap_node_free(root);
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}
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vieter_heap_node *vieter_heap_tree_merge_same_order(vieter_heap_node *root_a,
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vieter_heap_node *root_b) {
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vieter_heap_node *root, *child;
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if (root_a->key <= root_b->key) {
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root = root_a;
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child = root_b;
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} else {
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root = root_b;
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child = root_a;
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}
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child->ptr.next_largest_order = root->largest_order;
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root->largest_order = child;
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root->order++;
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return root;
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}
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vieter_heap_node *vieter_heap_tree_merge(vieter_heap_node *target_tree,
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vieter_heap_node *other_tree) {
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vieter_heap_node *out = target_tree;
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vieter_heap_node *next_other_tree, *next_target_tree;
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vieter_heap_node *previous_target_tree = NULL;
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while (target_tree != NULL && other_tree != NULL) {
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if (target_tree->order == other_tree->order) {
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next_other_tree = other_tree->ptr.next_tree;
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next_target_tree = target_tree->ptr.next_tree;
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target_tree = vieter_heap_tree_merge_same_order(target_tree, other_tree);
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target_tree->ptr.next_tree = next_target_tree;
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// If this merge produces a binomial tree whose size is already in
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// target, it will be the next target. Therefore, we can merge target's
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// trees until we no longer have a duplicate depth.
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while (next_target_tree != NULL &&
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next_target_tree->order == target_tree->order) {
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next_target_tree = next_target_tree->ptr.next_tree;
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target_tree = vieter_heap_tree_merge_same_order(
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target_tree, target_tree->ptr.next_tree);
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target_tree->ptr.next_tree = next_target_tree;
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}
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if (previous_target_tree != NULL) {
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previous_target_tree->ptr.next_tree = target_tree;
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} else {
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out = target_tree;
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}
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other_tree = next_other_tree;
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} else if (target_tree->order > other_tree->order) {
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next_other_tree = other_tree->ptr.next_tree;
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if (previous_target_tree == NULL) {
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previous_target_tree = other_tree;
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out = other_tree;
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} else {
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previous_target_tree->ptr.next_tree = other_tree;
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// This single missing line right here broke this entire function for
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// nearly a week.
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previous_target_tree = other_tree;
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}
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other_tree->ptr.next_tree = target_tree;
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other_tree = next_other_tree;
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} else {
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if (previous_target_tree == NULL) {
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out = target_tree;
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}
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previous_target_tree = target_tree;
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target_tree = target_tree->ptr.next_tree;
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}
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}
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// Append final part of tree to target
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if (target_tree == NULL) {
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previous_target_tree->ptr.next_tree = other_tree;
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}
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return out;
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}
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vieter_heap_node *vieter_heap_tree_pop(void **out, vieter_heap_node *tree) {
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vieter_heap_node *tree_before_smallest = NULL;
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vieter_heap_node *previous_tree = NULL;
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vieter_heap_node *original_root = tree;
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uint64_t smallest_key = tree->key;
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while (tree->ptr.next_tree != NULL) {
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previous_tree = tree;
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tree = tree->ptr.next_tree;
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if (tree->key < smallest_key) {
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smallest_key = tree->key;
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tree_before_smallest = previous_tree;
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}
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}
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vieter_heap_node *tree_to_pop;
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if (tree_before_smallest != NULL) {
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tree_to_pop = tree_before_smallest->ptr.next_tree;
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tree_before_smallest->ptr.next_tree = tree_to_pop->ptr.next_tree;
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} else {
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tree_to_pop = original_root;
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original_root = original_root->ptr.next_tree;
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}
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*out = tree_to_pop->data;
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if (tree_to_pop->order == 0) {
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vieter_heap_tree_free(tree_to_pop);
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return original_root;
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}
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// Each child has a pointer to its sibling with the next largest order. If we
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// want to convert this list of children into their own tree, these pointers
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// have to be reversed.
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previous_tree = tree_to_pop->largest_order;
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vieter_heap_node_free(tree_to_pop);
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tree = previous_tree->ptr.next_largest_order;
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previous_tree->ptr.next_tree = NULL;
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vieter_heap_node *next_tree;
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while (tree != NULL) {
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next_tree = tree->ptr.next_largest_order;
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tree->ptr.next_tree = previous_tree;
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previous_tree = tree;
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tree = next_tree;
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}
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// original_root is zero if the heap only contained a single tree.
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if (original_root != NULL) {
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return vieter_heap_tree_merge(original_root, previous_tree);
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} else {
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return previous_tree;
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}
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}
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