Questions that I had on (G**R**A**B) Online test

[akki-pesit]

Please add these questions to the list:

1. Light bulb 3
2. Find the longest distinct path starting from the root in a binary tree. All values in the path must be distinct.
3. https://leetcode.com/discuss/interview-question/1330993/how-to-find-a-node-in-graph-which-is-reachable-from-every-other-node-in-graph