Referred by a Googler. It took about two or three days before HR contacted me. Then, an interview time was arranged. There were two back-to-back tech interviews, each lasting 45 minutes. They focused mainly on algorithms. The interviewers were both nice and polite. The code was written in a Google Doc and communication was over the phone.

Given a string, we can "shift" each of its letters to its successive letter. For example: "abc" becomes "bcd". We can keep "shifting", which forms the sequence:

"abc" -> "bcd" -> ... -> "xyz"

Given a list of strings that contains only lowercase alphabets, group all strings that belong to the same shifting sequence.

For example, given: ["abc", "bcd", "acef", "xyz", "az", "ba", "a", "z"].

Return: [ ["abc","bcd","xyz"], ["az","ba"], ["acef"], ["a","z"] ]

Given a string, find the length of the longest substring T that contains at most M distinct characters.