I had a phone screen and then a standard HackerRank interview that went quite well (or so I thought). The next day, I was contacted and told they weren't moving forward.

I was kind of thrown off. This was the first experience where I walked out of an interview and guessed the outcome incorrectly. The interviewer wasn't familiar with C++, and although I solved their coding problem with the fastest runtime and articulated myself clearly, I guess this wasn't enough.

I asked for feedback afterward and was met with radio silence. I suspect something else may be at play here.

Given a 2D matrix of numbers, find the minimum cost path from the first row to the bottom row. The cost is the sum of the cells you traverse.