swap-nodes-in-pairs

19.remove-nth-node-from-end-of-list.js

-/*
- * @lc app=leetcode id=19 lang=javascript
- *
- * [19] Remove Nth Node From End of List
- *
- * https://leetcode.com/problems/remove-nth-node-from-end-of-list/description/
- *
- * algorithms
- * Medium (34.03%)
- * Total Accepted:    360.1K
- * Total Submissions: 1.1M
- * Testcase Example:  '[1,2,3,4,5]\n2'
- *
- * Given a linked list, remove the n-th node from the end of list and return
- * its head.
- * 
- * Example:
- * 
- * 
- * Given linked list: 1->2->3->4->5, and n = 2.
- * 
- * After removing the second node from the end, the linked list becomes
- * 1->2->3->5.
- * 
- * 
- * Note:
- * 
- * Given n will always be valid.
- * 
- * Follow up:
- * 
- * Could you do this in one pass?
- * 
- */
-/**
- * Definition for singly-linked list.
- * function ListNode(val) {
- *     this.val = val;
- *     this.next = null;
- * }
- */
-/**
- * @param {ListNode} head
- * @param {number} n
- * @return {ListNode}
- */
-var removeNthFromEnd = function(head, n) {
-    
-};
-

README.md

@@ -9,5 +9,6 @@ leetcode题解，记录自己的leecode解题之路。
 - [3. Longest Substring Without Repeating Characters](https://github.com/azl397985856/leetcode/blob/master/longestSubstringWithoutRepeatingCharacters.md)
 - [5. Longest Palindromic Substring](https://github.com/azl397985856/leetcode/blob/master/longestPalindromicSubstring.md)
 - [19. Remove Nth Node From End of List](https://github.com/azl397985856/leetcode/blob/master/removeNthNodeFromEndofList.md)
+- [24. Swap Nodes In Pairs](https://github.com/azl397985856/leetcode/blob/master/swapNodesInPairs.md)
 
 ### 高级难度
\ No newline at end of file

swapNodesInPairs.md

+## 题目地址
+https://leetcode.com/problems/swap-nodes-in-pairs/description/
+
+## 题目描述
+Given a linked list, swap every two adjacent nodes and return its head.
+
+You may not modify the values in the list's nodes, only nodes itself may be changed.
+
+ 
+
+Example:
+
+Given 1->2->3->4, you should return the list as 2->1->4->3.
+## 思路
+
+设置一个dummy 节点简化操作。  
+
+设置一个虚拟头结点dummyHead
+
+设置需要交换的两个节点分别为node1、node2，同时设置node2的下一个节点next
+
+在这一轮操作中
+将node2节点的next设置为node1节点
+
+将node1节点的next设置为next节点
+
+将dummyHead节点的next设置为node2
+
+结束本轮操作
+
+接下来的每轮操作都按照上述进行。
+
+![24.swap-nodes-in-pairs](./assets/24.swap-nodes-in-pairs.gif)
+
+(图片来自： https://github.com/MisterBooo/LeetCodeAnimation)
+
+## 关键点解析
+
+1. 链表这种数据结构的特点和使用
+
+2. dummyHead简化操作
+
+## 代码
+```js
+/*
+ * @lc app=leetcode id=24 lang=javascript
+ *
+ * [24] Swap Nodes in Pairs
+ *
+ * https://leetcode.com/problems/swap-nodes-in-pairs/description/
+ *
+ * algorithms
+ * Medium (43.33%)
+ * Total Accepted:    287.2K
+ * Total Submissions: 661.3K
+ * Testcase Example:  '[1,2,3,4]'
+ *
+ * Given a linked list, swap every two adjacent nodes and return its head.
+ *
+ * You may not modify the values in the list's nodes, only nodes itself may be
+ * changed.
+ *
+ *
+ *
+ * Example:
+ *
+ *
+ * Given 1->2->3->4, you should return the list as 2->1->4->3.
+ *
+ */
+/**
+ * Definition for singly-linked list.
+ * function ListNode(val) {
+ *     this.val = val;
+ *     this.next = null;
+ * }
+ */
+/**
+ * @param {ListNode} head
+ * @return {ListNode}
+ */
+var swapPairs = function(head) {
+  const dummy = new ListNode(0);
+  dummy.next = head;
+  let current = dummy;
+  while (current.next != null && current.next.next != null) {
+    const first = current.next;
+    const second = current.next.next;
+    first.next = second.next;
+    current.next = second;
+    current.next.next = first;
+    current = current.next.next;
+  }
+  return dummy.next;
+};
+
+```