forked from vieter-v/libvieter
143 lines
3.9 KiB
C
143 lines
3.9 KiB
C
#include "vieter_tree_balancing.h"
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bool vieter_tree_node_validate(vieter_tree_node *node,
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uint64_t passed_black_nodes,
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uint64_t expected_black_nodes) {
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// Path to NULL children should contain the same amount of black nodes
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if (node == NULL) {
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return passed_black_nodes == expected_black_nodes;
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}
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if (vieter_tree_node_get(node, vieter_tree_node_black)) {
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passed_black_nodes++;
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}
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// Either the node itself is black, or its children are both either NULL or
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// black.
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bool correctly_colored_children =
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vieter_tree_node_get(node, vieter_tree_node_black) ||
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((node->left == NULL ||
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vieter_tree_node_get(node->left, vieter_tree_node_black)) &&
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(node->right == NULL ||
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vieter_tree_node_get(node->right, vieter_tree_node_black)));
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return correctly_colored_children &&
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vieter_tree_node_validate(node->left, passed_black_nodes,
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expected_black_nodes) &&
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vieter_tree_node_validate(node->right, passed_black_nodes,
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expected_black_nodes);
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}
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vieter_tree_node *vieter_tree_node_balance(vieter_tree_node *node) {
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vieter_tree_node *parent = node->parent;
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vieter_tree_node *grand_parent = parent->parent;
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vieter_tree_node *root = grand_parent;
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vieter_tree_node *left, *right;
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vieter_tree_node *children[4];
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uint64_t key_root = root->key;
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void *data_root = root->data;
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if (node->key < parent->key && parent->key < grand_parent->key) {
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root->key = parent->key;
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root->data = parent->data;
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parent->key = key_root;
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parent->data = data_root;
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left = node;
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right = parent;
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children[0] = node->left;
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children[1] = node->right;
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children[2] = parent->right;
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children[3] = grand_parent->right;
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} else if (node->key < parent->key && parent->key > grand_parent->key) {
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root->key = node->key;
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root->data = node->data;
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node->key = key_root;
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node->data = data_root;
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left = node;
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right = parent;
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children[0] = grand_parent->left;
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children[1] = node->left;
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children[2] = node->right;
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children[3] = parent->right;
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} else if (node->key > parent->key && parent->key < grand_parent->key) {
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root->key = node->key;
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root->data = node->data;
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node->key = key_root;
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node->data = data_root;
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left = parent;
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right = node;
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children[0] = parent->left;
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children[1] = node->left;
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children[2] = node->right;
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children[3] = grand_parent->right;
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} else {
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root->key = parent->key;
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root->data = parent->data;
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parent->key = key_root;
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parent->data = data_root;
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left = parent;
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right = node;
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children[0] = grand_parent->left;
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children[1] = parent->left;
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children[2] = node->left;
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children[3] = node->right;
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}
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vieter_tree_node_set(left, vieter_tree_node_black);
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vieter_tree_node_set(right, vieter_tree_node_black);
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vieter_tree_node_unset(root, vieter_tree_node_black);
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left->left = children[0];
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left->right = children[1];
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if (children[0] != NULL)
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children[0]->parent = left;
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if (children[1] != NULL)
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children[1]->parent = left;
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right->left = children[2];
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right->right = children[3];
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if (children[2] != NULL)
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children[2]->parent = right;
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if (children[3] != NULL)
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children[3]->parent = right;
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root->left = left;
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root->right = right;
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left->parent = root;
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right->parent = root;
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return root;
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}
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void vieter_tree_node_balance_after_insert(vieter_tree_node *node) {
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while (!vieter_tree_node_get(node, vieter_tree_node_black) &&
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node->parent != NULL &&
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!vieter_tree_node_get(node->parent, vieter_tree_node_black)) {
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node = vieter_tree_node_balance(node);
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}
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// The root must always be black
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if (node->parent == NULL) {
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vieter_tree_node_set(node, vieter_tree_node_black);
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}
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}
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void vieter_tree_node_remove_balanced(vieter_tree_node *node) {}
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