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题目描述

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 `jth` 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`.

例子

例子 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 ]`

例子 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]`

例子 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.

解题思路

• 时间复杂度:`O(n*||V|+|E||)`
• 空间复杂度:`O(||V|+|E||)`

GitHub 代码同步地址： 399.EvaluateDivision.cpp

GitHub: Leetcode-C++-Solution