This content originally appeared on DEV Community 👩‍💻👨‍💻 and was authored by dominikbraun
graph is a Go library for creating generic graph data structures and modifying, analyzing, and visualizing them.
Features
- Generic vertices of any type, such as
intorCity. - Graph traits with corresponding validations, such as cycle checks in acyclic graphs.
- Algorithms for finding paths or components, such as shortest paths or strongly connected components.
- Algorithms for transformations and representations, such as transitive reduction or topological order.
- Algorithms for non-recursive graph traversal, such as DFS or BFS.
- Edges with optional metadata, such as weights or custom attributes.
- Visualization of graphs using the DOT language and Graphviz.
- Extensive tests with ~90% coverage, and zero dependencies.
Status: Because
graphis in version 0, the public API shouldn't be considered stable.
Getting started
go get github.com/dominikbraun/graph
Quick examples
Create a graph of integers
g := graph.New(graph.IntHash)
g.AddVertex(1)
g.AddVertex(2)
g.AddVertex(3)
g.AddVertex(4)
g.AddVertex(5)
_ = g.AddEdge(1, 2)
_ = g.AddEdge(1, 4)
_ = g.AddEdge(2, 3)
_ = g.AddEdge(2, 4)
_ = g.AddEdge(2, 5)
_ = g.AddEdge(3, 5)
Create a directed acyclic graph of integers
g := graph.New(graph.IntHash, graph.Directed(), graph.Acyclic())
g.AddVertex(1)
g.AddVertex(2)
g.AddVertex(3)
g.AddVertex(4)
_ = g.AddEdge(1, 2)
_ = g.AddEdge(1, 3)
_ = g.AddEdge(2, 3)
_ = g.AddEdge(2, 4)
_ = g.AddEdge(3, 4)
Create a graph of a custom type
To understand this example in detail, see the concept of hashes.
type City struct {
Name string
}
cityHash := func(c City) string {
return c.Name
}
g := graph.New(cityHash)
g.AddVertex(london)
Create a weighted graph
g := graph.New(cityHash, graph.Weighted())
g.AddVertex(london)
g.AddVertex(munich)
g.AddVertex(paris)
g.AddVertex(madrid)
_ = g.AddEdge("london", "munich", graph.EdgeWeight(3))
_ = g.AddEdge("london", "paris", graph.EdgeWeight(2))
_ = g.AddEdge("london", "madrid", graph.EdgeWeight(5))
_ = g.AddEdge("munich", "madrid", graph.EdgeWeight(6))
_ = g.AddEdge("munich", "paris", graph.EdgeWeight(2))
_ = g.AddEdge("paris", "madrid", graph.EdgeWeight(4))
Perform a Depth-First Search
This example traverses and prints all vertices in the graph in DFS order.
g := graph.New(graph.IntHash, graph.Directed())
g.AddVertex(1)
g.AddVertex(2)
g.AddVertex(3)
g.AddVertex(4)
_ = g.AddEdge(1, 2)
_ = g.AddEdge(1, 3)
_ = g.AddEdge(3, 4)
_ = graph.DFS(g, 1, func(value int) bool {
fmt.Println(value)
return false
})
1 3 4 2
Find strongly connected components
g := graph.New(graph.IntHash)
// Add vertices and edges ...
scc, _ := graph.StronglyConnectedComponents(g)
fmt.Println(scc)
[[1 2 5] [3 4 8] [6 7]]
Find the shortest path
g := graph.New(graph.StringHash, graph.Weighted())
// Add vertices and weighted edges ...
path, _ := graph.ShortestPath(g, "A", "B")
fmt.Println(path)
[A C E B]
Perform a topological sort
g := graph.New(graph.IntHash, graph.Directed(), graph.Acyclic())
// Add vertices and weighted edges ...
order, _ := graph.TopologicalSort(g)
fmt.Println(order)
[1 2 3 4 5]
Cycle checks for acyclic graphs
g := graph.New(graph.IntHash, graph.Acyclic())
g.AddVertex(1)
g.AddVertex(2)
g.AddVertex(3)
_ = g.AddEdge(1, 2)
_ = g.AddEdge(1, 3)
if err := g.AddEdge(2, 3); err != nil {
panic(err)
}
panic: an edge between 2 and 3 would introduce a cycle
Visualize a graph using Graphviz
The following example will generate a DOT description for g and write it into the given file.
g := graph.New(graph.IntHash, graph.Directed())
g.AddVertex(1)
g.AddVertex(2)
g.AddVertex(3)
_ = g.AddEdge(1, 2)
_ = g.AddEdge(1, 3)
file, _ := os.Create("./mygraph.gv")
_ = draw.DOT(g, file)
To generate an SVG from the created file using Graphviz, use a command such as the following:
dot -Tsvg -O mygraph.gv
Setting edge attributes
Edges may have one or more attributes which can be used to store metadata. Attributes will be taken
into account when visualizing a graph. For example, this edge
will be rendered in red color:
_ = g.AddEdge(1, 2, graph.EdgeAttribute("color", "red"))
To get an overview of all supported attributes, take a look at the
DOT documentation.
Concepts
Hashes
A graph consists of nodes (or vertices) of type T, which are identified by a hash value of type
K. The hash value is obtained using the hashing function passed to graph.New.
Primitive types
For primitive types such as string or int, you may use a predefined hashing function such as
graph.IntHash – a function that takes an integer and uses it as a hash value at the same time:
g := graph.New(graph.IntHash)
This also means that only one vertex with a value like
5can exist in the graph if
graph.IntHashused.
Custom types
For storing custom data types, you need to provide your own hashing function. This example function
takes a City and returns the city name as an unique hash value:
cityHash := func(c City) string {
return c.Name
}
Creating a graph using this hashing function will yield a graph with vertices of type City
identified by hash values of type string.
g := graph.New(cityHash)
Traits
The behavior of a graph, for example when adding or retrieving edges, depends on its traits. You
can set the graph's traits using the functional options provided by this library:
g := graph.New(graph.IntHash, graph.Directed(), graph.Weighted())
Documentation
The full documentation is available at pkg.go.dev.
Check out graph on GitHub: dominikbraun/graph
This content originally appeared on DEV Community 👩‍💻👨‍💻 and was authored by dominikbraun
dominikbraun | Sciencx (2022-09-14T17:24:44+00:00) graph: A library for creating generic graph data structures and modifying, analyzing, and visualizing them.. Retrieved from https://www.scien.cx/2022/09/14/graph-a-library-for-creating-generic-graph-data-structures-and-modifying-analyzing-and-visualizing-them/
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