题目：

题解：

class Solution:def calcEquation(self, equations: List[List[str]], values: List[float], queries: List[List[str]]) -> List[float]:# 构造图graph = defaultdict(list)for (u, v), value in zip(equations, values):graph[u].append((v, value))graph[v].append((u, 1 / value))def dfs(node, target, visited, acc_product):# 如果找到了目标节点，返回累积乘积if node == target:return acc_product# 标记当前节点为已访问visited.add(node)# 遍历当前节点的邻居for neighbor, value in graph[node]:if neighbor not in visited:result = dfs(neighbor, target, visited, acc_product * value)if result != -1:return resultreturn -1results = []for start, end in queries:if start in graph and end in graph:# 如果起点和终点都在图中，进行DFSresults.append(dfs(start, end, set(), 1.0))else:# 否则，结果为-1results.append(-1.0)return results