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use ego_tree::{NodeMut, NodeRef, Tree};
pub struct BinaryTree<T> {
inner: Tree<Option<T>>,
}
impl<T> BinaryTree<T> {
pub fn new(root_value: T) -> Self {
let mut tree = Tree::new(Some(root_value));
let mut root = tree.root_mut();
root.append(None);
root.append(None);
Self { inner: tree }
}
pub fn root(&self) -> BinaryNodeRef<T> {
BinaryNodeRef::wrap(self.inner.root())
}
pub fn root_mut(&mut self) -> BinaryNodeMut<T> {
BinaryNodeMut::wrap(self.inner.root_mut())
}
}
#[derive(Debug, PartialEq, Clone, Copy)]
pub struct BinaryNodeRef<'a, T> {
inner: NodeRef<'a, Option<T>>,
}
impl<'a, T> BinaryNodeRef<'a, T> {
pub fn left(&self) -> Option<BinaryNodeRef<'a, T>> {
let left = self.inner.children().next().expect("always has children");
if left.value().is_none() {
return None;
}
Some(BinaryNodeRef::wrap(left))
}
pub fn right(&self) -> Option<BinaryNodeRef<'a, T>> {
let mut children = self.inner.children();
let _left = children.next().expect("always has children");
let right = children.next().expect("always has children");
if right.value().is_none() {
return None;
}
Some(BinaryNodeRef::wrap(right))
}
pub fn value(&self) -> &T {
self.inner.value().as_ref().expect("exists")
}
fn wrap(node: NodeRef<'a, Option<T>>) -> Self {
Self { inner: node }
}
}
#[derive(Debug)]
pub struct BinaryNodeMut<'a, T> {
inner: NodeMut<'a, Option<T>>,
}
impl<'a, T> BinaryNodeMut<'a, T> {
fn left_inner(&mut self) -> NodeMut<Option<T>> {
self.inner.first_child().expect("exists")
}
fn right_inner(&mut self) -> NodeMut<Option<T>> {
self.inner.last_child().expect("exists")
}
pub fn left(&mut self) -> Option<BinaryNodeMut<T>> {
let mut left_inner = self.left_inner();
if left_inner.value().is_none() {
return None;
}
Some(BinaryNodeMut::wrap(left_inner))
}
pub fn right(&mut self) -> Option<BinaryNodeMut<T>> {
let mut right_inner = self.right_inner();
if right_inner.value().is_none() {
return None;
}
Some(BinaryNodeMut::wrap(right_inner))
}
pub fn value(&mut self) -> &mut T {
self.inner.value().as_mut().expect("exists")
}
pub fn set_right(&mut self, value: T) -> BinaryNodeMut<T> {
let mut right_inner = self.right_inner();
*right_inner.value() = Some(value);
if !right_inner.has_children() {
right_inner.append(None);
right_inner.append(None);
}
BinaryNodeMut::wrap(right_inner)
}
pub fn set_left(&mut self, value: T) -> BinaryNodeMut<T> {
let mut left_inner = self.left_inner();
*left_inner.value() = Some(value);
if !left_inner.has_children() {
left_inner.append(None);
left_inner.append(None);
}
BinaryNodeMut::wrap(left_inner)
}
fn wrap(node: NodeMut<'a, Option<T>>) -> Self {
Self { inner: node }
}
}
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn binary_tree_api_works() {
let mut tree = BinaryTree::new(5);
assert!(tree.root_mut().left().is_none());
assert!(tree.root_mut().right().is_none());
let mut root = tree.root_mut();
let mut left = root.set_left(3);
assert_eq!(left.value(), &3);
assert!(left.left().is_none());
assert!(left.right().is_none());
}
}