🐮 Update Readme

Author: 6boris

README-List.md

@@ -10,13 +10,17 @@ LeetCode of algorithms with golang solution(updating).
 
 ## List
 
-| #    | Title                                    | Tag                                      |
-| :--- | :--------------------------------------- | :--------------------------------------- |
-| 1    | [Two Sum][0001]                           | Array, Hash Table                        |
-| 7    | [Reverse Integer][0007]                   | Math                                     |
-| 9    | [Palindrome Number][0009]                 | Math                                     |
-| 13   | [Roman to Integer][0013]                  | Math, String                             |
-| 14   | [Longest Common Prefix][0014]             | String                                   |
+| #    | Title                                    | Tag                                      | Difficulty 	|
+| :--- | :--------------------------------------- | :--------------------------------------- | :----------- |
+| 1    | [Two Sum][0001]                           | Array, Hash Table                        | Easy		|
+| 7    | [Reverse Integer][0007]                   | Math                                     | Easy		|
+| 9    | [Palindrome Number][0009]                 | Math                                     |Easy		    |
+| 13   | [Roman to Integer][0013]                  | Math, String                             | Easy		|
+| 14   | [Longest Common Prefix][0014]             | Stack, String                            | Easy		|
+| 20   | [Valid Parentheses][0020]                  | Linked List                             | Easy		|
+| 21   | [Merge Two Sorted Lists][0021]             |Linked List                              | Easy		|
+| 26   | [Remove Duplicates from Sorted Array][0026]  | Array, Two Pointers                   | Easy		|
+| 27   | [Remove Element][0027]                     |  Array, Two Pointers                    | Easy		|
 
 
 
@@ -29,4 +33,8 @@ LeetCode of algorithms with golang solution(updating).
 [0009]: https://github.com/kylesliu/awesome-golang-leetcode/tree/master/src/0009.Palindrome-Number
 [0013]: https://github.com/kylesliu/awesome-golang-leetcode/tree/master/src/0013.Roman-to-Integer
 [0014]: https://github.com/kylesliu/awesome-golang-leetcode/tree/master/src/0014.Longest-Common-Prefix
+[0020]: https://github.com/kylesliu/awesome-golang-leetcode/tree/master/src/0020.Valid-Parentheses
+[0021]: https://github.com/kylesliu/awesome-golang-leetcode/tree/master/src/0021.Merge-Two-Sorted-Lists
+[0026]: https://github.com/kylesliu/awesome-golang-leetcode/tree/master/src/0026.Remove-Duplicates-from-Sorted-Array
+[0027]: https://github.com/kylesliu/awesome-golang-leetcode/tree/master/src/0027.Remove-Element