Graph theory, please

Had a tech interview at one of the big tech companies in silicon valley. The person presented the question, we chatted a bit about the problem so that I was sure I understood the conditions.

I then set about solving the problem talking my way through it as I went about 15 mins into the 50 min interview process the person realizes I am using backtracking to solve the problem and tells me they want a graph based solution because they work in machine learning and they are very familiar with graphs.

At this point I am mentally invested in my backtracking solution, it was a very non-trivial problem and I need to pull out of my though pattern and figure out how to solve the problem using graphs, something I have not touched in years. Needless to say it went downhill from there, I just could not visualize how to solve the problem with graphs and even talking through it with the person made little progress.

By Anonymous