Evaluate query ratios from equations

Problem Statement

You are given a list of equations equations, where each equations[i] = [A, B] represents the ratio A / B = values[i], and a list of queries queries, where each queries[j] = [C, D] asks for the result of C / D. If the result cannot be determined, return -1.0.

Each input A, B, C, D is a string representing a variable name, and values is a list of floating-point numbers. Always return the answer as a float. If a variable is not present in the equations or if there is no path between two variables, return -1.0.

Constraints

• 1 <= equations.length <= 20
• equations[i].length == 2
• values.length == equations.length
• 0.0 < values[i] <= 20.0
• queries.length <= 20

Example

Input: equations = [["a", "b"], ["b", "c"]], values = [2.0, 3.0], queries = [["a", "c"], ["b", "a"], ["a", "e"]]

Output: [6.0, 0.5, -1.0]

Explanation:

• a / c = (a / b) * (b / c) = 2.0 * 3.0 = 6.0
• b / a = 1 / (a / b) = 1 / 2.0 = 0.5
• e is unknown, so result is -1.0

Function Signature

def calcEquation(equations, values, queries):
    pass