1） Alien Dictionary
There is a new alien language which uses the latin alphabet. However, the order among letters are unknown to you. You receive a list of words from the dictionary, wherewords are sorted lexicographically by the rules of this new language. Derive the order of letters in this language.
For example,
Given the following words in dictionary,
[
"wrt",
"wrf",
"er",
"ett",
"rftt"
]
The correct order is: "wertf".
Note:
You may assume all letters are in lowercase.
If the order is invalid, return an empty string.
There may be multiple valid order of letters, return any one of them is fine.

Well, this problem is not that easy. First you may need some clarifications about the problem itself. If you do, you may refer to this post for a nice example which illustrates the purpose of this problem:
https://discuss.leetcode.com/topic/22395/the-description-is-wrong/3
Moreover, you need to understand graph representation, graph traversal and specifically, topological sort, which are all needed to solve this problem cleanly.

2） Text Justification
Given an array of words and a length L, format the text such that each line has exactly L characters and is fully (left and right) justified.
You should pack your words in a greedy approach; that is, pack as many words as you can in each line. Pad extra spaces ' ' when necessary so that each line has exactly L characters.

Extra spaces between words should be distributed as evenly as possible. If the number of spaces on a line do not divide evenly between words, the empty slots on the left will be assigned more spaces than the slots on the right.

For the last line of text, it should be left justified and no extra space is inserted between words.
For example,
words: ["This", "is", "an", "example", "of", "text", "justification."]
L: 16.
Return the formatted lines as:
[
"This is an",
"example of text",
"justification. "
]
Note: Each word is guaranteed not to exceed L in length.

3） Write an echo TCP client, send request to a given server, return back the response. Imagine you are driving a car, when you step on the gas, the car speed up, when you release, the car slow down. The client requests have 2 scenarios: （a）STATUS - query the current speed and the step pressure（b）THROTTLE 50.1 - adjust the pressure to 50.1
EXAMPLE: in telnet:
STATUS
0.0 0.0 (server return values, the first value is pressure, the second value is speed)
THROTTLE 50.1 (no server response here)
STATUS
50.1 3.75 (speed up)
STATUS (status again)
50.1 15.98 (speed going up still)

write a TCP client, write a function to control the speed to a given target speed

There is also a core value interview:
1）what bring you to airbnb?
2) what can you teach your co-workers after you get in?
3) describe a person whom you admire most
4) describe your experience with airbnb
5) where have you been to?
6) what will you do if you win a lottery such as Powerball?
7) what is the biggest fear in your life?
8 ) how do describe Airbnb to a people back to 2003?
9) if you have a book that writes about your whole life, will you read it? why?
10) if you have a time machine, and you can either go back or go forth, will you choose to go back or to go forth?
11) among all the features of airbnb, what do you want to improve?
12) describe a thing that is very risky to you, how did you deal with it?