It is less difficult than I thought. There are three rounds of 45-minute interview.

In the first round, I was asked to reverse a linked list with O(n) and O(1) space. You can do it with an extra pointer to store the next successor.
I was also asked to find the intersaction of two linked list. I was given the head of the two linked list. You can use a hashset to store the nodes in the first linked list, and return the first node that has been stored in such hashset when you traverse the second linked list.

In the second interview, I was asked about OOP concept like polymorphism and overriding. I was asked the same linked lists intersaction problem in the interview. LOL.
After that I was asked to implement a^b. You can do it in O(b) or O(log b) if you use divide-and-conquer.
I was asked to demonstrate some sorting algorithms too. I used bubble sort and merge sort as example.

In the last interview I was asked to do https://leetcode.com/problems/longest-palindromic-substring/, which is more interesting. I just used a O(n^3) method, but you can do it in O(n^2) with DP or exhausting the center of palindromic substring.