Samsung Electronics Software Developer interview questions

The interview was online and the interviewer asked me to write a program which I have done but the complexity of the program was O(n^2) and he asked me to do it in O(n) which I was not able to. And then he told me to wrap up the interview and I was not able to understand how he is able to judge me by asking only one question. However, I thought okay, no problem and I have asked him about the solution of the problem and I was surprised to hear his it because it was also O(n^2) but since he is an interviewer I can't argue with him.