Scotiabank Software Developer In Test interview questions

Multiple rounds. 1st round 30 min of phone screening with recruiter. 2nd interview with Senior Manager for about 44 mins. 3rd interview for 1 hr with 2 SDETs. 1st and 2nd rounds were good but in the 3rd round the SDETs assessing me did not initially understood the implementation of my code and asked me why I used a hashmap. I had to explain one of them that hashmap's don't allow duplicate keys and just update the value of key if it is added again. Also had to explain them the time complexity is an O(n) I was not given any reason for the rejection.