forked from vieter-v/libvieter
96 lines
2.4 KiB
C
96 lines
2.4 KiB
C
#include "balancing.h"
|
|
|
|
vieter_tree_node *vieter_tree_node_balance(vieter_tree_node *node) {
|
|
vieter_tree_node *parent = node->parent;
|
|
vieter_tree_node *grand_parent = parent->parent;
|
|
vieter_tree_node *grand_grand_parent = grand_parent->parent;
|
|
vieter_tree_node *root, *left, *right;
|
|
vieter_tree_node *children[4];
|
|
|
|
if (node->key < parent->key && parent->key < grand_parent->key) {
|
|
root = parent;
|
|
left = node;
|
|
right = grand_parent;
|
|
|
|
children[0] = node->left;
|
|
children[1] = node->right;
|
|
children[2] = parent->right;
|
|
children[3] = grand_parent->right;
|
|
} else if (node->key < parent->key && parent->key > grand_parent->key) {
|
|
root = node;
|
|
left = grand_parent;
|
|
right = parent;
|
|
|
|
children[0] = grand_parent->left;
|
|
children[1] = node->left;
|
|
children[2] = node->right;
|
|
children[3] = parent->right;
|
|
} else if (node->key > parent->key && parent->key < grand_parent->key) {
|
|
root = node;
|
|
left = parent;
|
|
right = grand_parent;
|
|
|
|
children[0] = parent->left;
|
|
children[1] = node->left;
|
|
children[2] = node->right;
|
|
children[3] = grand_parent->right;
|
|
} else {
|
|
root = parent;
|
|
left = grand_parent;
|
|
right = node;
|
|
|
|
children[0] = grand_parent->left;
|
|
children[1] = parent->left;
|
|
children[2] = node->left;
|
|
children[3] = node->right;
|
|
}
|
|
|
|
vieter_tree_node_set(left, vieter_node_black);
|
|
vieter_tree_node_set(right, vieter_node_black);
|
|
vieter_tree_node_unset(root, vieter_node_black);
|
|
|
|
left->left = children[0];
|
|
left->right = children[1];
|
|
|
|
if (children[0] != NULL)
|
|
children[0]->parent = left;
|
|
|
|
if (children[1] != NULL)
|
|
children[1]->parent = left;
|
|
|
|
right->left = children[2];
|
|
right->right = children[3];
|
|
|
|
if (children[2] != NULL)
|
|
children[2]->parent = right;
|
|
|
|
if (children[3] != NULL)
|
|
children[3]->parent = right;
|
|
|
|
root->left = left;
|
|
root->right = right;
|
|
left->parent = root;
|
|
right->parent = root;
|
|
|
|
if (grand_grand_parent != NULL) {
|
|
vieter_tree_node_add_child(grand_grand_parent, root->key, root);
|
|
} else {
|
|
root->parent = NULL;
|
|
}
|
|
|
|
return root;
|
|
}
|
|
|
|
void vieter_tree_node_balance_after_insert(vieter_tree_node *node) {
|
|
while (!vieter_tree_node_get(node, vieter_node_black) &&
|
|
node->parent != NULL &&
|
|
!vieter_tree_node_get(node->parent, vieter_node_black)) {
|
|
node = vieter_tree_node_balance(node);
|
|
}
|
|
|
|
// The root must always be black
|
|
if (node->parent == NULL) {
|
|
vieter_tree_node_set(node, vieter_node_black);
|
|
}
|
|
}
|