Modified Bus Routes Minimum Changes | Dataford Interview Questions

Modified Bus Routes: each bus runs its route in an infinite loop; find the minimum number of bus changes to reach the destination from the source.

Asked in the Coding stage.

Implement min_bus_changes(routes, source, destination). routes[i] lists the stops served by bus i; return the minimum changes, or -1 if unreachable. Staying at the source requires 0 changes.

Examples:

[[1, 2, 7], [3, 6, 7]], 1, 6 returns 1.
[[1, 2], [3, 4]], 1, 4 returns -1.

Constraints

1 <= routes.length <= 500
1 <= routes[i].length <= 10^4
1 <= routes[i][j] <= 10^6
A route may contain repeated stops.
Return 0 when source equals destination.
Return -1 when the destination is unreachable.

Function Signature

def min_bus_changes(routes, source, destination):

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