IBM Engineer 01 interview questions

I got an online screener for SWE, US Hackerrank. The screener was a mystery, with no real indication of what facet of ComSci you should be bringing with you. It was graph theory, I was rusty on that. First question involves finding the minimum edges between all nodes in a connected graph. the second question involves building and traversing a bigraph. Paraphrased, of course. You could probably do this in the allotted hour if you were familiar and fresh on the material.