basic btree works
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9f09799413
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d63222a6ef
1 changed files with 99 additions and 15 deletions
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@ -1,9 +1,20 @@
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use std::mem;
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use crate::vec::Vec;
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pub const DEFAULT_DEGREE: usize = 1;
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#[derive(Clone, Debug)]
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pub struct BTree<T> {
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pub struct BTree<T: Ord + Clone> {
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root: Node<T>,
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properties: BTreeProperties,
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}
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#[derive(Clone, Debug, Copy)]
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pub struct BTreeProperties {
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degree: usize,
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max_keys: usize,
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mid_key_index: usize,
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}
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#[derive(Clone, Debug)]
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@ -12,6 +23,63 @@ struct Node<T> {
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children: Vec<Node<T>>,
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}
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impl BTreeProperties {
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fn new(degree: usize) -> Self {
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Self {
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degree,
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max_keys: degree - 1,
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mid_key_index: (degree - 1) / 2,
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}
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}
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fn split_child<T: Ord + Clone>(&self, parent: &mut Node<T>, child_index: usize) {
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let child = &mut parent.children[child_index];
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let middle_key: T = child.keys[self.mid_key_index].clone();
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let right_keys = match child.keys.split_off(self.mid_key_index).split_first() {
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Some((_first, _others)) => {
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// We don't need _first, as it will move to parent node.
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_others.into()
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}
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None => Vec::<T>::with_capacity(self.max_keys),
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};
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let right_children = if !child.is_leaf() {
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Some(child.children.split_off(self.mid_key_index + 1))
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} else {
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None
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};
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let new_child_node: Node<T> = Node::new(self.degree, Some(right_keys), right_children);
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parent.keys.insert(child_index, middle_key);
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parent.children.insert(child_index + 1, new_child_node);
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}
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fn is_maxed_out<T: Ord>(&self, node: &Node<T>) -> bool {
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node.keys.len() == self.max_keys
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}
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fn insert_non_full<T: Ord + Clone>(&mut self, node: &mut Node<T>, key: T) {
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let mut index: isize = isize::try_from(node.keys.len()).ok().unwrap() - 1;
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while index >= 0 && node.keys[index as usize] >= key {
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index -= 1;
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}
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let mut u_index: usize = usize::try_from(index + 1).ok().unwrap();
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if node.is_leaf() {
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// Just insert it, as we know this method will be called only when node is not full
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node.keys.insert(u_index, key);
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} else {
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if self.is_maxed_out(&node.children[u_index]) {
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self.split_child(node, u_index);
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if node.keys[u_index] < key {
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u_index += 1;
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}
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}
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self.insert_non_full(&mut node.children[u_index], key);
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}
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}
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}
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impl<T> Node<T>
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where
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T: Ord,
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@ -34,47 +102,63 @@ where
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}
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}
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impl<T: Ord> BTree<T> {
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impl<T: Ord + Clone> BTree<T> {
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pub fn new(branch_factor: usize) -> Self {
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let degree = 2 * branch_factor;
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Self {
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root: Node::new(degree, None, None),
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degree,
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properties: BTreeProperties::new(degree),
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}
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}
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pub fn clear(&mut self) {
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self.root = Node::new(self.degree, None, None);
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self.root = Node::new(self.properties.degree, None, None);
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}
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fn rebalance() {
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todo!()
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pub fn insert(&mut self, key: T) {
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if self.properties.is_maxed_out(&self.root) {
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// Create an empty root and split the old root...
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let mut new_root = Node::new(self.properties.degree, None, None);
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mem::swap(&mut new_root, &mut self.root);
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self.root.children.insert(0, new_root);
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self.properties.split_child(&mut self.root, 0);
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}
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self.properties.insert_non_full(&mut self.root, key)
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}
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pub fn insert(&mut self, value: T) -> Option<T> {
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todo!()
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}
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pub fn has(&self, value: T) -> bool {
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todo!()
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#[must_use]
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pub fn has(&self, key: T) -> bool {
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let mut current_node = &self.root;
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loop {
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match current_node.keys.binary_search(&key) {
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Ok(_) => return true,
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Err(idx) => {
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if current_node.is_leaf() {
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return false;
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}
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current_node = ¤t_node.children[idx];
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}
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}
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}
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}
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}
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#[cfg(test)]
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mod test {
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use super::*;
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#[test]
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fn test_create() {
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let _tree = BTree::<u32>::new();
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let _tree = BTree::<u32>::new(DEFAULT_DEGREE);
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}
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#[test]
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fn test_insert() {
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let mut tree = BTree::<u32>::new();
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let mut tree = BTree::<u32>::new(DEFAULT_DEGREE);
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let data = &[19, 125, 25, 16, 2, 73, 384, 435, 12924, 42, 125251, 2548];
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for d in data {
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assert!(tree.insert(*d).is_none())
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tree.insert(*d)
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}
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for d in data {
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