Evaluate query ratios from equations

You are given equations of the form `A / B = value` where `A` and `B` are variable names (strings) and `value` is a positive real number. You also receive queries of the form `X / Y = ?`. For each query, return the computed ratio if it can be derived from the known equations; otherwise return `-1.0`. **Input** - `equations`: list of pairs `[Ai, Bi]` - `values`: list of doubles where `values[i]` corresponds to `Ai / Bi` - `queries`: list of pairs `[Xj, Yj]` **Output** - Array of doubles where each element is the answer for the corresponding query. **Notes / Constraints** - Variables not appearing in any equation make related queries impossible. - You may assume there are no contradictions. - Aim for a graph + DFS/BFS solution. **Example** - `equations = [["a","b"],["b","c"]]`, `values = [2.0, 3.0]` - `queries = [["a","c"],["c","a"],["a","e"],["a","a"],["x","x"]]` - Output: `[6.0, 1/6, -1.0, 1.0, -1.0]`