From 52cbec304ec4c4530551612f4a26b7fb2a5108cd Mon Sep 17 00:00:00 2001
From: Jerry Zeng <87971517+Zzz212zzZ@users.noreply.github.com>
Date: Fri, 28 Feb 2025 00:31:03 -0500
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---
 problems/0707.设计链表.md | 154 ++++++++++++++++++++++++++++++++++
 1 file changed, 154 insertions(+)

diff --git a/problems/0707.设计链表.md b/problems/0707.设计链表.md
index ed1726d9..5c72b05a 100644
--- a/problems/0707.设计链表.md
+++ b/problems/0707.设计链表.md
@@ -1191,6 +1191,160 @@ MyLinkedList.prototype.deleteAtIndex = function(index) {
  */
 ```
 
+```js
+/** 
+    定义双头节点的结构：同时包含前指针`prev`和后指针next`
+*/
+class Node {
+    constructor(val, prev, next) {
+        this.val = val
+        this.prev = prev
+        this.next = next
+    }
+}
+
+/**
+    双链表：维护 `head` 和 `tail` 两个哨兵节点，这样可以简化对于中间节点的操作  
+    并且维护 `size`，使得能够以O(1)时间判断操作是否合法
+*/
+var MyLinkedList = function () {
+    this.tail = new Node(-1)
+    this.head = new Node(-1)
+    this.tail.prev = this.head
+    this.head.next = this.tail
+    this.size = 0
+};
+
+/** 
+ * 获取在index处节点的值
+ *
+ * @param {number} index
+ * @return {number}
+ *
+ * 时间复杂度: O(n)
+ * 空间复杂度: O(1)
+ */
+MyLinkedList.prototype.get = function (index) {
+    // 当索引超出范围时，返回-1
+    if (index > this.size) {
+        return -1
+    }
+
+    let cur = this.head
+    for (let i = 0; i <= index; i++) {
+        cur = cur.next
+    }
+
+    return cur.val
+};
+
+/**
+ * 在链表头部添加一个新节点
+ *
+ * @param {number} val
+ * @return {void}
+ * 
+ * 时间复杂度: O(1)
+ * 空间复杂度: O(1)
+ */
+MyLinkedList.prototype.addAtHead = function (val) {
+    /** 
+       head <-> [newNode] <-> originNode
+    */
+    this.size++
+    const originNode = this.head.next
+    // 创建新节点，并建立连接
+    const newNode = new Node(val, this.head, originNode)
+
+    // 取消原前后结点的连接
+    this.head.next = newNode
+    originNode.prev = newNode
+};
+
+/** 
+ * 在链表尾部添加一个新节点
+ *
+ * @param {number} val
+ * @return {void}
+ *
+ * 时间复杂度: O(1)
+ * 空间复杂度: O(1)
+ */
+MyLinkedList.prototype.addAtTail = function (val) {
+    /** 
+        originNode <-> [newNode] <-> tail
+    */
+    this.size++
+    const originNode = this.tail.prev
+
+    // 创建新节点，并建立连接
+    const newNode = new Node(val, originNode, this.tail)
+
+    // 取消原前后结点的连接
+    this.tail.prev = newNode
+    originNode.next = newNode
+};
+
+/** 
+ * 在指定索引位置前添加一个新节点
+ *
+ * @param {number} index 
+ * @param {number} val
+ * @return {void}
+ *
+ * 时间复杂度: O(n)
+ * 空间复杂度: O(1)
+ */
+MyLinkedList.prototype.addAtIndex = function (index, val) {
+    // 当索引超出范围时，直接返回
+    if (index > this.size) {
+        return
+    }
+    this.size++
+
+    let cur = this.head
+    for (let i = 0; i < index; i++) {
+        cur = cur.next
+    }
+
+    const new_next = cur.next
+
+    // 创建新节点，并建立连接
+    const node = new Node(val, cur, new_next)
+
+    // 取消原前后结点的连接
+    cur.next = node
+    new_next.prev = node
+};
+
+/**
+ * 删除指定索引位置的节点
+ *
+ * @param {number} index
+ * @return {void}
+ *
+ * 时间复杂度: O(n)
+ * 空间复杂度: O(1)
+ */
+MyLinkedList.prototype.deleteAtIndex = function (index) {
+    // 当索引超出范围时，直接返回
+    if (index >= this.size) {
+        return
+    }
+
+    this.size--
+    let cur = this.head
+    for (let i = 0; i < index; i++) {
+        cur = cur.next
+    }
+
+    const new_next = cur.next.next
+    // 取消原前后结点的连接
+    new_next.prev = cur
+    cur.next = new_next
+};
+```
+
 ### TypeScript:
 
 ```TypeScript