I had a technical phone interview for a software engineer position in the revenue group at LinkedIn. I was able to solve both problems asked by the engineer correctly. The problems were of average difficulty. We used Collabedit for the interview. The LinkedIn employee seemed satisfied with my solutions.

A few days later, I was told that they were passing on me with no feedback or reason explained. I learned (in part from the recruiter) that they were learning to test/interview software engineers with my skill set. I felt they were not honest and were using me as a guinea pig for their own purposes, possibly collecting interview data and doing this to many other people interviewing for this position. They may have been developing a corporate tool and testing it with real people, gathering data, and making candidates believe they were being considered for a software engineering position when they were not.

LinkedIn, please be serious. Stop playing games and wasting people's time. Do not use real people as guinea pigs for your models, studies, or corporate tools.

Problem using a Trie data structure to find all possible words occurring in a data set.

Output should be a set containing all words that occur in the data set.