Round 1:
a. OOD, design a furniture class. Requirement: type: table/chair, material: steer/wood, methods: addWeight/putFire, test the intensity of a furniture, check if a furniture is usable or not.

Round 2:
a. Basic data structure problems.
b. Stack with min
c. find common parts of two files (not sorted, files could be very large)

Round 3:
a. Merge two sorted array (and eliminate duplicates),
b. Letter Combinations of a Phone Number
Given a digit string, return all possible letter combinations that the number could represent.
Example: Inputsmilieigit string "23"
Output: ["ad", "ae", "af", "bd", "be", "bf", "cd", "ce", "cf"].
c. basic design pattern questions.

Round 4:
a. Given an array of intervals. Input: an integer, output: true if there exists at least one interval containing this integer.

Round 5:
Given a board with 0 and 1, find number of all components (connected 1s).
Example:
1 0 0 0
1 1 0 1
0 1 0 1
0 0 1 0
Output: 3.
Serialization/Deserialization of a Binary Tree.