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Implement BFS

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Your question is Implement BFS. Start with the requirements on the right.

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Problem

Air Space Intelligence's Flyways platform models airspace connections as a directed graph. Given the graph and two node identifiers, use breadth-first search to return the route with the fewest connections between the start and destination nodes.

Formal Specification

Implement shortest_route(graph, start, destination), where graph is a dictionary mapping each node identifier to a list of directly reachable node identifiers. Return a list containing the nodes in the shortest route, including both start and destination. If the destination cannot be reached, return an empty list. If start equals destination, return a list containing that node.

The graph may contain cycles. Do not revisit a node after it has been discovered. If multiple shortest routes exist, returning any one of them is valid.

Constraints

  • 1 <= number of nodes <= 10^5
  • 0 <= number of directed edges <= 2 * 10^5
  • Node identifiers are hashable and unique
  • Every neighbor appears as a key in graph
  • The graph can contain cycles and disconnected components

Function Signature

def shortest_route(graph, start, destination):
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