Qualtrics Software Engineer interview questions

I had been given the hacker rank as prescreen then I Interviewed onsite at seattle Office. Hacker Rank questions 1) Stickers 2) Delete and earn Onsite Questions I had 4 rounds 1) system design -- design slack messanger 2) Mgr -- culture fit round 3) Coding - Find common words from array of books -- get API will give words in book. -- follow up.. find top n common words.. [I did the sorting here.. but I guess he was expecting Priority Queue or something...I come from js script background.. so fancy data structures for me] -- Time complexity for the same 4) Coding -- Find the first effected node given a set of nodes. -- Get API will return if node is healthy or not also will return set of child nodes which all will have same health status of parent. -- Time Complexity for the same -- I find it simiar to journey problem to find the the starting node. used +1 for main node as source and -1 for all the child nodes as they represent destination. add them to dictory and result is the nodes with value >=0, Interviewer said he has not seen this type before. we ran couple of test cases , every thing was working as expected. -- follow up with more test cases and failure points in algo [API can error out]. I thought I did extremely well in all the rounds but they send me reject :( FML.

Had a phone interview that went well. Then I had 3 on-site interviews each 45 minutes long and those went well and then the next week a video interview which wasn't as positive.