| 7 | [重建二叉树](https://www.nowcoder.com/practice/8a19cbe657394eeaac2f6ea9b0f6fcf6?tpId=13&tqId=11157&tPage=1&rp=3&ru=%2Fta%2Fcoding-interviews&qru=%2Fta%2Fcoding-interviews%2Fquestion-ranking) | [105. Construct Binary Tree from Preorder and Inorder Traversal](solutions/105.%20Construct%20Binary%20Tree%20from%20Preorder%20and%20Inorder%20Traversal.md)|
| 9 | [用两个栈实现队列](https://www.nowcoder.com/practice/54275ddae22f475981afa2244dd448c6?tpId=13&tqId=11158&tPage=1&rp=3&ru=%2Fta%2Fcoding-interviews&qru=%2Fta%2Fcoding-interviews%2Fquestion-ranking) | [232. Implement Queue using Stacks](solutions/232.%20Implement%20Queue%20using%20Stacks.md)|