From 69a628df7270acde3cbd95daade9d278904c7d0b Mon Sep 17 00:00:00 2001
From: sunface <cto@188.com>
Date: Wed, 16 Mar 2022 16:05:23 +0800
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---
 src/SUMMARY.md                       |  1 +
 src/too-many-lists/deque/iterator.md | 26 ++++++++++++++++++++++++++
 2 files changed, 27 insertions(+)
 create mode 100644 src/too-many-lists/deque/iterator.md

diff --git a/src/SUMMARY.md b/src/SUMMARY.md
index b43507af..66539706 100644
--- a/src/SUMMARY.md
+++ b/src/SUMMARY.md
@@ -171,6 +171,7 @@
       - [数据布局和基本操作](too-many-lists/deque/layout.md)
       - [Peek](too-many-lists/deque/peek.md)
       - [基本操作的对称镜像](too-many-lists/deque/symmetric.md)
+      - [迭代器](too-many-lists/deque/iterator.md)
 - [易混淆概念解析](confonding/intro.md)
   - [切片和切片引用](confonding/slice.md)
   - [Eq 和 PartialEq](confonding/eq.md)
diff --git a/src/too-many-lists/deque/iterator.md b/src/too-many-lists/deque/iterator.md
new file mode 100644
index 00000000..51967d55
--- /dev/null
+++ b/src/too-many-lists/deque/iterator.md
@@ -0,0 +1,26 @@
+# 迭代器
+坏男孩最令人头疼，而链表实现中，迭代器就是这样的坏男孩，所以我们放在最后来处理。
+
+## IntoIter
+由于是转移所有权，因此 `IntoIter` 一直都是最好实现的:
+```rust
+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<T> {
+        self.0.pop_front()
+    }
+}
+```
+
+但是关于双向链表，有一个有趣的事实，它不仅可以从前向后迭代，还能反过来。前面实现的是传统的从前到后，那问题来了，反过来该如何实现呢？
+
+答案是: `DoubleEndedIterator`，它继承自 `Iterator`( 通过 [`supertrait`](https://course.rs/basic/trait/advance-trait.html?highlight=supertrait#特征定义中的特征约束) )，因此意味着要实现该特征，首先需要实现 `Iterator`。
+