feat: BFS with depth

[williamfzc]

Thanks for your awesome project :)

This PR enhances current hook function for controlling BFS processing. Such as, stop BFS at a specfic depth level.

I am not pretty sure if there is a existed way to achieve this. But currently I have to walk the whole graph even I only need the first 3 layers.

[dominikbraun]

Thanks for your PR! That makes perfectly sense. I only have one suggestion: Because the DFS and DFSWithDepth implementations are the same, you could remove the DFS function body and replace it with a call to DFSWithDepth:

ignoreDepth := func(vertex K, _ int) {
    visit(vertex)
}

return DFSWithDepth(g, start, ignoreDepth)

... or something like that.

[williamfzc]

Thanks for your PR! That makes perfectly sense. I only have one suggestion: Because the DFS and DFSWithDepth implementations are the same, you could remove the DFS function body and replace it with a call to DFSWithDepth:

ignoreDepth := func(vertex K, _ int) {
    visit(vertex)
}

return DFSWithDepth(g, start, ignoreDepth)

... or something like that.

Sorry I have forgot leaving a comment for notification :) Already modified.

[dominikbraun]

This change has been released in graph v0.21.0.