Problem - Evaluate Division

Given equations like $a/b = 2.0$ and $b/c = 3.0$, answer queries like $a/c = ?$ and $a/a = ?$.

Return $-1.0$ for undefined queries (variables not in equations or not connected).

Example:

equations = [["a","b"],["b","c"]]
values = [2.0, 3.0]
queries = [["a","c"],["b","a"],["a","e"]]
Output: [6.0, 0.5, -1.0]

$a/c = (a/b) \cdot (b/c) = 2 \cdot 3 = 6$

You're implementing weighted Union-Find: edge weights are division ratios.

Constraints: up to 20 equations and 20 queries.