Merge pull request #9 from programmingbookclub/meetup-20

Create LeetCode 讀書會第 20 次聚會 2021_01_26.md

Author: ytyubox

紀錄/LeetCode 讀書會第 20 次聚會 2021_01_26.md

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+# LeetCode 讀書會第 20 次聚會 2021/01/26
+
+leetcode 讀書會通知
+1. 項目: 第 20  次聚會
+2. 目的: 線上一起寫題目, 由有想法的人帶領, 先解題, 再看該題有趣的解法
+3. 時間: 1/26 (二) 20:00 ~ 21:00
+4. 地點: google meet 線上 (前 10 分鐘預備鏈接)
+5. 解題項目:  [Linked list - Doubly linked list](https://leetcode.com/explore/learn/card/linked-list/210/doubly-linked-list/)
+
+    ```text
+### Doubly Linked list
+  1. Medium 707. Design Linked List
+
+### Conclusion
+  1.  Easy 21. Merge Two Sorted Lists 
+  2. Medium    2. Add Two Numbers 
+  3. Medium    430. Flatten a Multilevel Doubly Linked 
+                                > List Hint: Try to solve this problem recursively.
+  4. Medium    708.  Insert into a Cyclic Sorted List 
+                                 >  Hint: A cyclic list here is a linked list that the last node is linked with the first node and form a cycle. Find out the smallest node will help you determine the suitable position.
+  5. Medium    138.  Copy List with Random Pointer 
+                                  > Hint: Using a hash set maybe is a good idea. Refer to our hash table card if you are not familiar with the hash set.
+  6. Medium    61.  Rotate List 
+    ```
+
+6. 共筆: GitHub https://github.com/programmingbookclub/Leetcode-club