[数据结构与算法]009 通过链表学习Rust之IntoIter

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

本节我们为链表实现迭代器。迭代器Trait的定义如下：

pub trait Iterator {
    type Item;
    fn next(&mut self) -> Option<Self::Item>;
}

对于我们来说，我们要实现以下三个迭代器：

IntoIter - T      //对应元素本身
IterMut - &mut T  //对应元素的可变引用
Iter - &T         //对应元素的引用

IntoIter

下面，我们先实现IntoIter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()
	}
}

测试与完整代码

加上测试的完整代码：

pub struct List<T> {
	head: Link<T>,
}

type Link<T> = Option<Box<Node<T>>>;

struct Node<T> {
	elem: T,
	next: Link<T>,
}

impl<T> List<T> {
	pub fn new() -> Self {
		List { head: None }
	}

	pub fn push(&mut self, elem: T) {
		let node = Box::new(Node{
			elem: elem,
			next: self.head.take(),
		});
		self.head = Some(node);
	}

	pub fn pop(&mut self) -> Option<T> {
		self.head.take().map(|node| {
			self.head = node.next;
			node.elem
		})
	}

	pub fn peek(&self) -> Option<&T> {
		//self.head.map(|node| {
		self.head.as_ref().map(|node| {
			&node.elem
		})
	}

	pub fn peek_mut(&mut self) -> Option<&mut T> {
		self.head.as_mut().map(|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()
	}
}

#[cfg(test)]
mod tests {
	use super::List;
    #[test]
	fn basics() {
        let mut list = List::new();
        assert_eq!(list.pop(), None);

        list.push(1);
        list.push(2);
        list.push(3);
        
        assert_eq!(list.pop(), Some(3));
        assert_eq!(list.pop(), Some(2));

        list.push(4);
        list.push(5);

        assert_eq!(list.pop(), Some(5));
        assert_eq!(list.pop(), Some(4));

        assert_eq!(list.pop(), Some(1));
        assert_eq!(list.pop(), None);
    }

	#[test]
	fn peek() {
	    let mut list = List::new();

	    assert_eq!(list.peek(), None);
	    assert_eq!(list.peek_mut(), None);
	    list.push(1); 
		list.push(2); 
		list.push(3);
		
	    assert_eq!(list.peek(), Some(&3));
	    assert_eq!(list.peek_mut(), Some(&mut 3));

		//list.peek_mut().map(|&mut value| {
		list.peek_mut().map(|value| { //取指针
			//value = 32
			*value = 32
		});

	    assert_eq!(list.peek(), Some(&32));
	    assert_eq!(list.pop(), Some(32));
	}

	#[test]
	fn into_iter() {
	    let mut list = List::new();
	    list.push(1); 
		list.push(2); 
		list.push(3);

	    let mut iter = list.into_iter();
	    assert_eq!(iter.next(), Some(3));
	    assert_eq!(iter.next(), Some(2));
	    assert_eq!(iter.next(), Some(1));
	    assert_eq!(iter.next(), None);
	}
}