The round started with an introduction of both myself and the interviewer. I was asked just one coding question in this round, I had to write a full working code on a shared coderPad. The question was given an arithmetic expression like 4+(5*2)/3-1, I had to determine whether the given arithmetic expression is valid or not. https://codereview.stackexchange.com/questions/181606/determine-if-simple-arithmetic-expression-is-valid/181657 I told him a stack-based approach he was satisfied, then he asked me to do it without using stack, I was able to code that too. Then for each of my approach, he gave 18-20 test cases to pass which were having different errors like unbalanced parenthesis or consecutive operands together ( 4++2) both of my approaches passed all the test cases Finally, he gave me 2 test cases that contained space like (4 2).. my stack solution gave the wrong answer for this I was going to rectify the solution but due to the paucity of time, he said its alright. I was selected for the next round.