ByteDance interview questions

I applied for the software engineer position by referral. I got an email to set up the first phone call with a recruiter. Then she scheduled the first round of technical interviews. The interviewer spoke Mandarin to me. In the beginning, he asked me questions based on my resume. Then he asked me why hashmap can perform O(1) time. Then he moved forward to a coding part. There were 2 leetcode medium problems. I solved both of them but for the first one, I used O(nlogn) algorithm instead of O(n) which is the optimal time complexity. Two days later, I got a rejection email.