Find degrees of connection in a LinkedIn graph

You are given an undirected graph representing professional connections: - `n` people labeled `0..n-1` - a list of undirected edges `connections`, where `(a, b)` means `a` and `b` are directly connected (1st-degree) Given two people `src` and `dst`, return the minimum number of connections (degrees) needed to reach `dst` from `src`: - return `0` if `src == dst` - return `1` if directly connected - return `2` if connected via one intermediate person, etc. - return `-1` if `dst` is not reachable from `src` Optionally (if asked), also return one shortest path. Constraints: `1 ≤ n ≤ 1e5`, `0 ≤ |connections| ≤ 2e5`. The solution should be efficient.