# All Pairs Shortest Path Problem

Graph is undirected, unweighted and acyclic . How to find distance between all pairs? What is fastest algo. I’m confused between floyd- warshall, bellman ford, Johnson and Dijkstra’s algos.
Any help would be appreciated.

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Floyd- Warshall will provide you with all pair shortest path

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complexity??
I want the fastest.

I think you can try bfs for every node ie O((e+v)^2)

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ok thank that is v^2 time complexity for all pairs can’t it be done in vlogv?

I don’t think so.

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ok thanks for help btw

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An undirected, unweighted and acyclic graph is a forest right. Isn’t using graph algorithms an overkill. I think It can be solved using lca in nlogn time. correct me if I am wrong.

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@triee, i think this is a better solution.

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ohk, I’ll try to learn about lca thanks
given graph is also connected so it is a tree basically
forest with only one connected component is a tree,right?

Forest consists of trees.

Yes.

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can you also tell in brief about lca and how to apply?