介绍
视频地址：https://www.bilibili.com/video/av78062009/
相关源码：https://github.com/anonymousGiga/Rust-link-list
详细内容
本节我们来为我们的双链表实现迭代器。
IntoIter
实现代码如下：
//实现IntoIter
pub struct IntoIter<T>(List<T>);
impl<T> List<T> {
pub fn into_iter(self) -> IntoIter<T> {
IntoIter(self)
}
}
impl<T> Iterator for IntoIter<T> {
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
self.0.pop_front()
}
}
impl<T> DoubleEndedIterator for IntoIter<T> {
fn next_back(&mut self) -> Option<T> {
self.0.pop_back()
}
}
测试代码
#[test]
fn into_iter() {
let mut list = List::new();
list.push_front(1);
list.push_front(2);
list.push_front(3);
let mut iter = list.into_iter();
assert_eq!(iter.next(), Some(3));
assert_eq!(iter.next_back(), Some(1));
assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next_back(), None);
assert_eq!(iter.next(), None);
}
完整代码
use std::rc::Rc;
use std::cell::{Ref, RefMut, RefCell};
pub struct List<T> {
head: Link<T>,
tail: Link<T>,
}
type Link<T> = Option<Rc<RefCell<Node<T>>>>;
struct Node<T> {
elem: T,
next: Link<T>,
prev: Link<T>,
}
impl<T> Node<T> {
fn new(elem: T) -> Rc<RefCell<Self>> {
Rc::new(RefCell::new(Node {
elem: elem,
prev: None,
next: None,
}))
}
}
impl<T> List<T> {
pub fn new() -> Self {
List { head: None, tail: None }
}
pub fn push_front(&mut self, elem: T) {
let node = Node::new(elem);
match self.head.take() {
Some(head) => {
//取可变引用使用borrow_mut
head.borrow_mut().prev = Some(node.clone());
node.borrow_mut().next = Some(head);
self.head = Some(node);
}
None => {
self.tail = Some(node.clone());
self.head = Some(node);
}
}
}
pub fn push_back(&mut self, elem: T) {
let node = Node::new(elem);
match self.tail.take() {
Some(tail) => {
//取可变引用使用borrow_mut
tail.borrow_mut().next = Some(node.clone());
node.borrow_mut().prev = Some(tail);
self.tail = Some(node);
}
None => {
self.head = Some(node.clone());
self.tail = Some(node);
}
}
}
pub fn pop_front(&mut self) -> Option<T> {
self.head.take().map(|node| {
match node.borrow_mut().next.take() {
Some(next) => {
next.borrow_mut().prev.take();
self.head = Some(next);
}
None => {
self.tail.take();
}
}
//取值使用into_inner
Rc::try_unwrap(node).ok().unwrap().into_inner().elem
})
}
pub fn pop_back(&mut self) -> Option<T> {
self.tail.take().map(|node| {
match node.borrow_mut().prev.take() {
Some(prev) => {
prev.borrow_mut().next.take();
self.tail = Some(prev);
}
None => {
self.head.take();
}
}
//取值使用into_inner
Rc::try_unwrap(node).ok().unwrap().into_inner().elem
})
}
//pub fn peek_front(&self) -> Option<&T> {
pub fn peek_front(&self) -> Option<Ref<T>> {
self.head.as_ref().map(|node| {
//node.borrow()
Ref::map(node.borrow(), |node| &node.elem)
})
}
pub fn peek_back(&self) -> Option<Ref<T>> {
self.tail.as_ref().map(|node| {
Ref::map(node.borrow(), |node| &node.elem)
})
}
pub fn peek_front_mut(&mut self) -> Option<RefMut<T>> {
self.head.as_ref().map(|node| {
RefMut::map(node.borrow_mut(), |node| &mut node.elem)
})
}
pub fn peek_back_mut(&mut self) -> Option<RefMut<T>> {
self.tail.as_ref().map(|node| {
RefMut::map(node.borrow_mut(), |node| &mut node.elem)
})
}
}
//实现IntoIter
pub struct IntoIter<T>(List<T>);
impl<T> List<T> {
pub fn into_iter(self) -> IntoIter<T> {
IntoIter(self)
}
}
impl<T> Iterator for IntoIter<T> {
type Item = T;
fn next(&mut self) -> Option<Self::Item> {
self.0.pop_front()
}
}
impl<T> DoubleEndedIterator for IntoIter<T> {
fn next_back(&mut self) -> Option<T> {
self.0.pop_back()
}
}
#[cfg(test)]
mod tests {
use super::List;
#[test]
fn basics() {
let mut list = List::new();
assert_eq!(list.pop_front(), None);
list.push_front(1);
list.push_front(2);
list.push_front(3);
assert_eq!(list.pop_front(), Some(3));
assert_eq!(list.pop_front(), Some(2));
list.push_front(4);
list.push_front(5);
assert_eq!(list.pop_front(), Some(5));
assert_eq!(list.pop_front(), Some(4));
assert_eq!(list.pop_front(), Some(1));
assert_eq!(list.pop_front(), None);
// ---- back -----
assert_eq!(list.pop_back(), None);
list.push_back(1);
list.push_back(2);
list.push_back(3);
assert_eq!(list.pop_back(), Some(3));
assert_eq!(list.pop_back(), Some(2));
list.push_back(4);
list.push_back(5);
assert_eq!(list.pop_back(), Some(5));
assert_eq!(list.pop_back(), Some(4));
assert_eq!(list.pop_back(), Some(1));
assert_eq!(list.pop_back(), None);
}
#[test]
fn peek() {
let mut list = List::new();
assert!(list.peek_front().is_none());
assert!(list.peek_back().is_none());
assert!(list.peek_front_mut().is_none());
assert!(list.peek_back_mut().is_none());
list.push_front(1); list.push_front(2); list.push_front(3);
assert_eq!(&*list.peek_front().unwrap(), &3);
assert_eq!(&mut *list.peek_front_mut().unwrap(), &mut 3);
assert_eq!(&*list.peek_back().unwrap(), &1);
assert_eq!(&mut *list.peek_back_mut().unwrap(), &mut 1);
}
#[test]
fn into_iter() {
let mut list = List::new();
list.push_front(1);
list.push_front(2);
list.push_front(3);
let mut iter = list.into_iter();
assert_eq!(iter.next(), Some(3));
assert_eq!(iter.next_back(), Some(1));
assert_eq!(iter.next(), Some(2));
assert_eq!(iter.next_back(), None);
assert_eq!(iter.next(), None);
}
}
