update readme

Author: hogan-tech

.github/Question List.txt

@@ -6,4 +6,5 @@
 
 0007-reverse-integer python medium
 0452-minimum-number-of-arrows-to-burst-balloons python medium
-0010-regular-expression-matching python hard
+0010-regular-expression-matching python hard
+1669-merge-in-between-linked-lists python medium

README.md

@@ -364,6 +364,7 @@ The solutions are organized as follows:
 | 1658 | [Minimum Operations to Reduce X to Zero](https://leetcode.com/problems/minimum-operations-to-reduce-x-to-zero/)                                                     | [Python](./1658-minimum-operations-to-reduce-x-to-zero/1658-minimum-operations-to-reduce-x-to-zero.py)                                                                                                                                                                         | [Medium](./1658-minimum-operations-to-reduce-x-to-zero/README.md)                         |
 | 1660 | [Correct a Binary Tree](https://leetcode.com/problems/correct-a-binary-tree/)                                                                                       | [Python](./1660-correct-a-binary-tree/1660-correct-a-binary-tree.py)                                                                                                                                                                                                           | [Medium](./1660-correct-a-binary-tree/README.md)                                          |
 | 1662 | [Check If Two String Arrays are Equivalent](https://leetcode.com/problems/check-if-two-string-arrays-are-equivalent/)                                               | [Python](./1662-check-if-two-string-arrays-are-equivalent/1662-check-if-two-string-arrays-are-equivalent.py)                                                                                                                                                                   | [Easy](./1662-check-if-two-string-arrays-are-equivalent/README.md)                        |
+| 1669 | [Merge In Between Linked Lists](https://leetcode.com/problems/merge-in-between-linked-lists/)                                                                       | [Python](./1669-merge-in-between-linked-lists/1669-merge-in-between-linked-lists.py)                                                                                                                                                                                           | [Medium](./1669-merge-in-between-linked-lists/README.md)                                  |
 | 1683 | [Invalid Tweets](https://leetcode.com/problems/invalid-tweets/)                                                                                                     | [SQL](./1683-invalid-tweets/1683-invalid-tweets.sql)                                                                                                                                                                                                                           | [Easy](./1683-invalid-tweets/README.md)                                                   |
 | 1685 | [Sum of Absolute Differences in a Sorted Array](https://leetcode.com/problems/sum-of-absolute-differences-in-a-sorted-array/)                                       | [Python](./1685-sum-of-absolute-differences-in-a-sorted-array/1685-sum-of-absolute-differences-in-a-sorted-array.py)                                                                                                                                                           | [Medium](./1685-sum-of-absolute-differences-in-a-sorted-array/README.md)                  |
 | 1688 | [Count of Matches in Tournament](https://leetcode.com/problems/count-of-matches-in-tournament/)                                                                     | [Python](./1688-count-of-matches-in-tournament/1688-count-of-matches-in-tournament.py)                                                                                                                                                                                         | [Easy](./1688-count-of-matches-in-tournament/README.md)                                   |