Extramarks Software Engineer - Java Developer interview questions

First round was online assessment 2nd was technical and 3rd was also technical. I don't know on which basis they reject any candidate as I was sure that I have answered the questions correctly 70-80%. If you want a candidate to be answerable 100% then it's very difficult to find such candidates because in IT it doesn't matter how much experienced you are but you can't be 100% knowledgeable.

1st round was online based on Coding, Java Fundamentals,Spring and Hibernate ! I scored 71% marks in that. Got selected for the next and final round. Interviewer asked for my project and Java questions and i gave all the answers correctly. Then he asked me 1 coding ques to find smallest missing positive no,i gave him approach with O(n) space and time ,he said do it in O(1) space So I gave him the solution for that as well but he keep on saying that it won't work but I was confident , i had done dry run for all the test cases that he provided and it worked but he still said it won't work but did not give me any case or reason where it will fail. I also cross checked my approach by submitting the code on leetcode after interview and it got accepted !! He just want the solution that he came prepared with ! At last he said ur problem solving skills are good. And then i got the result that I am rejected. Looks like he was deliberately looking for a reason to reject,I am not sure why !!! They didn't give me the feedback as well. I had given around 20-30 interviews till now but this was the worst experience that you are rejecting without any reason.