OA, Hirevue, Techincal interview. The Interviewer started asking my about my project and stuff at the start, then we got into coding. For the TI, the email said prepare stats, and plotting library so i was expecting a time series analysis question, but interviewer went straight into a leetcode style question, and ask me about the time complexity of the algorithm. Since my background is in data analysis which he is aware of and thats what i was told to prepare), i didnt know how to use random off the top of my head, asked to used documentation (which email said it was allowed), he refused to let me and said code it from scratch which i did. Then he asked me about the time complexity of this mapping of random array, i brought it up to him multiple times that i said i didnt know what it was, but then he start guiding me how to calculate, which resulted in the harmonic series. he then told me to calcluate the sum of the harmonic series off my head from n = 1 -> 100. i started guessing as who could ? then he said if im guess above the answer he'll just interview here (which he did).