Graphs

Implement an algorithm to create a deep copy of a graph, including all nodes and edges, while preserving the original structure.

There are n cities connected by flights, where flights[i] = [from, to, price]. Given src, dst, and an integer k, return the cheapest total price to travel from src to dst using at most k stops (intermediate cities), or -1 if there is no such route.

You are given an m x n grid where each cell is 0 (empty), 1 (a fresh orange), or 2 (a rotten orange). Every minute, any fresh orange that is 4-directionally adjacent to a rotten orange becomes rotten. Return the minimum number of minutes that must elapse until no cell has a fresh orange, or -1 if this is impossible.

You are given a list of division equations. Each pair equations[i] = [A, B] with the corresponding values[i] = v encodes the relation A / B = v. For each query [C, D], compute C / D using whatever chain of equations is needed; if it cannot be derived, return -1.0. Solve by modeling variables as nodes in a directed weighted graph and traversing (BFS/DFS) to compute query ratios.