Emailed back and forth to schedule a phone interview. Got a call from a senior Data Scientist who asked me a few related algorithm questions. By the end, the questions were complicated enough where it became difficult to describe over the phone. I was able to answer all questions (though I required a hint for one), and he then congratulated me on surviving the ksum question.

First question: You have an array of numbers. Find all pairs that add up to K.

Second question: You have an array of numbers. Find all three-element groups that add up to K.

Third question: You have an array of numbers. Find all four-element groups that add up to K.

For all these questions, I had to provide a running time.