Deepmap挂经

申请的是Deepmap的Embedded Systems Software Engineer岗位，电话面试自己准备的不好答得不好，4天后收到拒信。

问题大概是：
1、What’s the difference between threads and processes.
2、What is reference in c++
3、If multiple threads access one variable, what should we do(mutex).
然后在线考了一道简单算法题，用C++写mirror a binary tree