update readme

Author: hogan-tech

.github/Question List.txt

@@ -6,4 +6,5 @@
 
 2331-evaluate-boolean-binary-tree python easy
 1325-delete-leaves-with-a-given-value python medium
-0979-distribute-coins-in-binary-tree python medium
+0979-distribute-coins-in-binary-tree python medium
+3068-find-the-maximum-sum-of-node-values python hard

README.md

@@ -562,6 +562,7 @@ The solutions are organized as follows:
 | 3005 | [Count Elements with Maximum Frequency](https://leetcode.com/problems/count-elements-with-maximum-frequency/)                                                       | [Python](./3005-count-elements-with-maximum-frequency/3005-count-elements-with-maximum-frequency.py)                                                                                                                                                                           | [Easy](./3005-count-elements-with-maximum-frequency/README.md)                            |
 | 3062 | [Winner of the Linked List Game](https://leetcode.com/problems/winner-of-the-linked-list-game/)                                                                     | [Python](./3062-winner-of-the-linked-list-game/3062-winner-of-the-linked-list-game.py)                                                                                                                                                                                         | [Easy](./3062-winner-of-the-linked-list-game/README.md)                                   |
 | 3063 | [Linked List Frequency](https://leetcode.com/problems/linked-list-frequency/)                                                                                       | [Python](./3063-linked-list-frequency/3063-linked-list-frequency.py)                                                                                                                                                                                                           | [Medium](./3063-linked-list-frequency/README.md)                                          |
+| 3068 | [Find the Maximum Sum of Node Values](https://leetcode.com/problems/find-the-maximum-sum-of-node-values/)                                                           | [Python](./3068-find-the-maximum-sum-of-node-values/3068-find-the-maximum-sum-of-node-values.py)                                                                                                                                                                               | [Hard](./3068-find-the-maximum-sum-of-node-values/README.md)                              |
 | 3075 | [Maximize Happiness of Selected Children](https://leetcode.com/problems/maximize-happiness-of-selected-children/)                                                   | [Python](./3075-maximize-happiness-of-selected-children/3075-maximize-happiness-of-selected-children.py)                                                                                                                                                                       | [Medium](./3075-maximize-happiness-of-selected-children/README.md)                        |
 
 ## How to Use