Coding: Leetcode 1290, 1779, 239. For 1779 and 239 they would push you to code in the dumb way first if you can't think of an optimized way. But they won't give you time to code the optimized way even if you got the idea. Short answers: 1.Difference between thread and process. 2. Suppose you have a static variable declared out side any functions in a C program, will the address be the same if it's declared in some function. 3. Will the address of a static variable always be the same between different runs of this program (no recompilation in between). 4. What's the difference between a real-time OS and a general purpose OS.
