2023-01-20 12:08:05 +01:00
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#include "balancing.h"
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2023-01-20 13:23:53 +01:00
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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 *grand_grand_parent = grand_parent->parent;
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vieter_tree_node *root, *left, *right;
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vieter_tree_node *children[4];
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if (node->key < parent->key && parent->key < grand_parent->key) {
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root = parent;
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left = node;
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right = grand_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 = node;
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left = grand_parent;
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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 = node;
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left = parent;
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right = grand_parent;
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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 = parent;
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left = grand_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_node_black);
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vieter_tree_node_set(right, vieter_node_black);
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vieter_tree_node_unset(root, vieter_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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if (grand_grand_parent != NULL) {
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vieter_tree_node_add_child(grand_grand_parent, root->key, root);
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} else {
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root->parent = NULL;
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}
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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_node_black) &&
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node->parent != NULL &&
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!vieter_tree_node_get(node->parent, vieter_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_node_black);
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}
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}
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