399.Evaluate Division
===

###### tags: `Medium`,`Array`,`Graph`,`DFS`,`BFS`

[399. Evaluate Division](https://leetcode.com/problems/evaluate-division/)

### 題目描述

You are given an array of variable pairs `equations` and an array of real numbers `values`, where `equations[i] = [Ai, Bi]` and `values[i]` represent the equation `Ai` / `Bi` = `values[i]`. Each `Ai` or `Bi` is a string that represents a single variable.

You are also given some `queries`, where `queries[j]` = `[Cj, Dj]` represents the j^th^ query where you must find the answer for `Cj` / `Dj` = ?.

Return *the answers to all queries.* If a single answer cannot be determined, return `-1.0`.

**Note:** The input is always valid. You may assume that evaluating the queries will not result in division by zero and that there is no contradiction.

### 範例

**Example 1:**

Input: equations = [["a","b"],["b","c"]], values = [2.0,3.0], queries = [["a","c"],["b","a"],["a","e"],["a","a"],["x","x"]]
Output: [6.00000,0.50000,-1.00000,1.00000,-1.00000]
Explanation: 
Given: a / b = 2.0, b / c = 3.0
queries are: a / c = ?, b / a = ?, a / e = ?, a / a = ?, x / x = ?
return: [6.0, 0.5, -1.0, 1.0, -1.0 ]

**Example 2:**

Input: equations = [["a","b"],["b","c"],["bc","cd"]], values = [1.5,2.5,5.0], queries = [["a","c"],["c","b"],["bc","cd"],["cd","bc"]]
Output: [3.75000,0.40000,5.00000,0.20000]

**Example 3:**

Input: equations = [["a","b"]], values = [0.5], queries = [["a","b"],["b","a"],["a","c"],["x","y"]]
Output: [0.50000,2.00000,-1.00000,-1.00000]

**Constraints**:

* 1 <= `equations.length` <= 20
* `equations[i].length` == 2
* 1 <= `Ai.length`, `Bi.length` <= 5
* `values.length` == `equations.length`
* 0.0 < `values[i]` <= 20.0
* 1 <= `queries.length` <= 20
* `queries[i].length` == 2
* 1 <= `Cj.length`, `Dj.length` <= 5
* `Ai`, `Bi`, `Cj`, `Dj` consist of lower case English letters and digits.

### 解答

### Reference

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