class Solution:

    def calcEquation(self, equations: List[List[str]], values: List[float], queries: List[List[str]]) -> List[float]:

        graph = {}

        for (x,y),v in zip(equations,values):

            if x not in graph:

                graph[x] = {y:v}

            else:

                graph[x][y] = v

            if y not in graph:

                graph[y] = {x:1/v}

            else:

                graph[y][x] = 1/v

        def dfs(x,y):

            if x not in graph:

                return -1

            if x == y:

                return 1

            for node in graph[x].keys():

                if node == y:

                    return graph[x][node]

                elif node not in visited:

                    visited.add(node)

                    v = dfs(node,y)

                    if v!= -1:

                        return graph[x][node]*v

            return -1

        res = []

        for x,y in queries:

            visited = set()

            res.append(dfs(x,y))

        return res