Graph-Based Problem Solution | Dataford Interview Questions

Shopee Express operates transfer routes between numbered sorting hubs. Each route moves a parcel directly from one hub to another and counts as one transfer. Given the directed routes, return the minimum number of transfers needed to move a parcel from source to destination. Return -1 if the destination is unreachable.

Formal Specification

Implement minimum_transfers(n, routes, source, destination), where n is the number of hubs labeled 0 through n - 1, and routes is a list of directed pairs [u, v] indicating a route from hub u to hub v. Return an integer representing the minimum number of routes on a valid path from source to destination.

Routes may be repeated, and the graph may contain cycles. A hub can be visited at most once during the search.

Constraints

1 <= n <= 10^5
0 <= routes.length <= 2 * 10^5
Each route contains exactly two integers [u, v]
0 <= u, v < n
0 <= source, destination < n
Routes are directed and may be repeated

Function Signature

def minimum_transfers(n, routes, source, destination):

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