IXL Learning Software Engineer Intern interview questions

I was offered an interview by IXL a week or so after a career fair at my university. The interviewer was very friendly, and had been on the IXL team for several years. She told me a bit more about the company, asked if I had any questions, and gave me a programming problem to do on paper. I got the sense that she really liked working for IXL.

I applied online and I get the email from HR to schedule a phone interview. The interview is from a engineer, after some behavior questions, he gave a technical question: give an Integer array with length n, and all value between 0 to n-1, detect if there is a duplication in the array. After this I got very quick response to schedule the next interview. The same format as last one. But he ask more about the projects listed in my CV. The technical question is that given an String array, group all anagrams together. To be fair, the interview is not hard. But regretfully I didn't do well in the second one (I think communication is the reason but I'm not sure :)), and after one week they decided to not move on with me, Generally the interview process is nice, and the interviewers are very kind especially the first one in my experience.