除法求值

399. 除法求值 (Medium)

给出方程式 A / B = k, 其中 A 和 B 均为用字符串表示的变量, k 是一个浮点型数字。根据已知方程式求解问题,并返回计算结果。如果结果不存在,则返回 -1.0

输入总是有效的。你可以假设除法运算中不会出现除数为 0 的情况,且不存在任何矛盾的结果。

 

示例 1:

输入:equations = [["a","b"],["b","c"]], values = [2.0,3.0], queries = [["a","c"],["b","a"],["a","e"],["a","a"],["x","x"]]
输出:[6.00000,0.50000,-1.00000,1.00000,-1.00000]
解释:
给定:a / b = 2.0, b / c = 3.0
问题:a / c = ?, b / a = ?, a / e = ?, a / a = ?, x / x = ?
返回:[6.0, 0.5, -1.0, 1.0, -1.0 ]

示例 2:

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

示例 3:

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

 

提示:

  • 1 <= equations.length <= 20
  • equations[i].length == 2
  • 1 <= equations[i][0].length, equations[i][1].length <= 5
  • values.length == equations.length
  • 0.0 < values[i] <= 20.0
  • 1 <= queries.length <= 20
  • queries[i].length == 2
  • 1 <= queries[i][0].length, queries[i][1].length <= 5
  • equations[i][0], equations[i][1], queries[i][0], queries[i][1] 由小写英文字母与数字组成

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