I answered this way in C# private static bool IsBalanced(string input) { int balance = 0; foreach(char c in input) { if(c=='{') balance +=1; else if (c=='}') balance -=1; if(balance < 0) return false; } return (balance==0); } It worked like a charm, with minimum code, to the satisfaction of the interviewer. He tested the input string something like this: "Hello {this} is {a} test" - return true. "Hello {{this} is} {a} test" - return false. Not balanced, since you have two openning braces, "{{this}" although the count is zero. It is still considered not balanced. Next, I met RF group. Question include about RF, amplifier, 1 dB Compression Point, Third Order Intercept, Noise Figure, PIM etc. As far as S-Parameters, I don't think they know a lot about Network Analyzer, PNA or VNA, ( They don't know anything about group delay, loss slope, delay slope, input/output return loss of a passive RF device.) Next, I met the SW group. They ask typical question such as how do you write a program from start to finish. I answer first gather the requirements, then gather all the dependencies, such as drivers for the instruments, manuals, DLL etc, design architecture (block diagram, front end, backend etc..) hold discussions, meetings and reviews, before writing a single line of code.Depending if you are the solo developer or part of a team, you should be able to code, debug, release, document, train people how to use it, push to repository etc.. Anyways, after everything is said and done, expect to be discriminated if you don't fall within their little clique. Good Luck!