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<main>
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<h1 id="基本操作的对称镜像"><a class="header" href="#基本操作的对称镜像">基本操作的对称镜像</a></h1>
|
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<p>之前我们仅实现了头部的 <code>push</code>、<code>pop</code> ，现在来补全一下，大自然的对称之美咱的双向链表也不能少了。</p>
|
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<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
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|
</span><span class="boring">fn main() {
|
|
|
</span>tail <-> head
|
|
|
next <-> prev
|
|
|
front -> back
|
|
|
<span class="boring">}</span></code></pre></pre>
|
|
|
<p>需要注意的是，这里还新增了 <code>mut</code> 类型的 peek:</p>
|
|
|
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
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|
</span><span class="boring">fn main() {
|
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|
</span>use std::cell::{Ref, RefCell, RefMut};
|
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|
//..
|
|
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|
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pub fn push_back(&mut self, elem: T) {
|
|
|
let new_tail = Node::new(elem);
|
|
|
match self.tail.take() {
|
|
|
Some(old_tail) => {
|
|
|
old_tail.borrow_mut().next = Some(new_tail.clone());
|
|
|
new_tail.borrow_mut().prev = Some(old_tail);
|
|
|
self.tail = Some(new_tail);
|
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|
}
|
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|
None => {
|
|
|
self.head = Some(new_tail.clone());
|
|
|
self.tail = Some(new_tail);
|
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|
}
|
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|
}
|
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}
|
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pub fn pop_back(&mut self) -> Option<T> {
|
|
|
self.tail.take().map(|old_tail| {
|
|
|
match old_tail.borrow_mut().prev.take() {
|
|
|
Some(new_tail) => {
|
|
|
new_tail.borrow_mut().next.take();
|
|
|
self.tail = Some(new_tail);
|
|
|
}
|
|
|
None => {
|
|
|
self.head.take();
|
|
|
}
|
|
|
}
|
|
|
Rc::try_unwrap(old_tail).ok().unwrap().into_inner().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_back_mut(&mut self) -> Option<RefMut<T>> {
|
|
|
self.tail.as_ref().map(|node| {
|
|
|
RefMut::map(node.borrow_mut(), |node| &mut 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)
|
|
|
})
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre></pre>
|
|
|
<p>再更新测试用例:</p>
|
|
|
<pre><pre class="playground"><code class="language-rust edition2021"><span class="boring">#![allow(unused)]
|
|
|
</span><span class="boring">fn main() {
|
|
|
</span>#[test]
|
|
|
fn basics() {
|
|
|
let mut list = List::new();
|
|
|
|
|
|
// Check empty list behaves right
|
|
|
assert_eq!(list.pop_front(), None);
|
|
|
|
|
|
// Populate list
|
|
|
list.push_front(1);
|
|
|
list.push_front(2);
|
|
|
list.push_front(3);
|
|
|
|
|
|
// Check normal removal
|
|
|
assert_eq!(list.pop_front(), Some(3));
|
|
|
assert_eq!(list.pop_front(), Some(2));
|
|
|
|
|
|
// Push some more just to make sure nothing's corrupted
|
|
|
list.push_front(4);
|
|
|
list.push_front(5);
|
|
|
|
|
|
// Check normal removal
|
|
|
assert_eq!(list.pop_front(), Some(5));
|
|
|
assert_eq!(list.pop_front(), Some(4));
|
|
|
|
|
|
// Check exhaustion
|
|
|
assert_eq!(list.pop_front(), Some(1));
|
|
|
assert_eq!(list.pop_front(), None);
|
|
|
|
|
|
// ---- back -----
|
|
|
|
|
|
// Check empty list behaves right
|
|
|
assert_eq!(list.pop_back(), None);
|
|
|
|
|
|
// Populate list
|
|
|
list.push_back(1);
|
|
|
list.push_back(2);
|
|
|
list.push_back(3);
|
|
|
|
|
|
// Check normal removal
|
|
|
assert_eq!(list.pop_back(), Some(3));
|
|
|
assert_eq!(list.pop_back(), Some(2));
|
|
|
|
|
|
// Push some more just to make sure nothing's corrupted
|
|
|
list.push_back(4);
|
|
|
list.push_back(5);
|
|
|
|
|
|
// Check normal removal
|
|
|
assert_eq!(list.pop_back(), Some(5));
|
|
|
assert_eq!(list.pop_back(), Some(4));
|
|
|
|
|
|
// Check exhaustion
|
|
|
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);
|
|
|
}
|
|
|
<span class="boring">}</span></code></pre></pre>
|
|
|
<p>什么？你问我这里的测试用例全吗？只能说如果测试全部的组合情况，这一章节会被撑爆。至于现在，能不出错就谢天谢地了 :(</p>
|
|
|
<pre><code class="language-shell">$ cargo test
|
|
|
|
|
|
Running target/debug/lists-5c71138492ad4b4a
|
|
|
|
|
|
running 10 tests
|
|
|
test first::test::basics ... ok
|
|
|
test fourth::test::basics ... ok
|
|
|
test second::test::basics ... ok
|
|
|
test fourth::test::peek ... ok
|
|
|
test second::test::iter ... ok
|
|
|
test third::test::iter ... ok
|
|
|
test second::test::into_iter ... ok
|
|
|
test second::test::iter_mut ... ok
|
|
|
test second::test::peek ... ok
|
|
|
test third::test::basics ... ok
|
|
|
|
|
|
test result: ok. 10 passed; 0 failed; 0 ignored; 0 measured
|
|
|
</code></pre>
|
|
|
<p>我想说：Ctrl CV 是最好的编程工具，大家同意吗？</p>
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