Query edges from/to given vertex

[wylswz]

Is it possible to add methods like this to Graph[K, T]

EdgesFrom(sourceHash K) ([]Edge[K], error)
EdgesTo(targetHash K) ([]Edge[K], error)

Currently I need to fetch all edges, and filter them by Target and Source property, which doesn't seem to scale

[dominikbraun]

Would using the adjacency and predecessor maps work for you?

adjacencyMap, _ := g.AdjacencyMap()

for target, edge := adjacencyMap[myVertex] {
    // This is an outgoing edge of myVertex.
    fmt.Println(edge)
}

predecessorMap, _ := g. PredecessorMap()

for source, edge := predecessorMap[myVertex] {
    // This is an ingoing edge of myVertex.
    fmt.Println(edge)
}

[wylswz]

That computes maps from scratch every time, still get O(V+E) time complexity

    for _, vertex := range vertices {
        m[vertex] = make(map[K]Edge[K])
    }

    for _, edge := range edges {
        m[edge.Source][edge.Target] = edge
    }

I can add some caches for now (given that my graph isn't updated very frequently)

[wylswz]

Tested out cached adjMap & predMap solution, that worked fine for me. Thanks for your reply, will close this issue

[dominikbraun]

@wylswz Your suggestion of adding functions like EdgesFrom is good though, I'm going to dig into it.