1。binary tree where every node has a color. Calculate the number of
disjoint three adjacent nodes.
2. timer problem：use semaphore in ISR to wake up a user function call.
三个组面试。最后一个组的manager很热情。这个manager同hr最后问：salary
expectation, preferences on which of those three groups in interview。
Salary expectation: 就说接受standard package，但没有给具体数据。最后hr问了一
下我现在的工资。Manager很想我给一个数据。
Preference on which group:回答都喜欢。
不清楚该怎样回答。
