Harshy interview

I have given 5 rounds of interview consisting of four technicals and hr round. My first three round was buttery smooth and i performed outstanding. In the last round i did made the solution as per the interviewer wants but i solved the question through other methods in the same time and space complexity. Verdict : got rejected. I know that interviewer know only one method and he wants me to do in that way.. how can i do that things ? Well the company was EDS backed by northern trust was interviewing for junior full stack developer. Such a harsh way to reject candidate.