List all vertex sets that are minimal (s,t) separators for some s and t, in an undirected graph.

## Usage

min_st_separators(graph)

## Arguments

graph

The input graph. It may be directed, but edge directions are ignored.

## Value

A list of numeric vectors. Each vector contains a vertex set (defined by vertex ids), each vector is an (s,t) separator of the input graph, for some $$s$$ and $$t$$.

## Details

A $$(s,t)$$ vertex separator is a set of vertices, such that after their removal from the graph, there is no path between $$s$$ and $$t$$ in the graph.

A $$(s,t)$$ vertex separator is minimal if none of its subsets is an $$(s,t)$$ vertex separator.

## References

Anne Berry, Jean-Paul Bordat and Olivier Cogis: Generating All the Minimal Separators of a Graph, In: Peter Widmayer, Gabriele Neyer and Stephan Eidenbenz (editors): Graph-theoretic concepts in computer science, 1665, 167--172, 1999. Springer.

## Author

Gabor Csardi csardi.gabor@gmail.com

## Examples

ring <- make_ring(4)
min_st_separators(ring)
#> [[1]]
#> + 2/4 vertices, from 4b29dc7:
#> [1] 2 4
#>
#> [[2]]
#> + 2/4 vertices, from 4b29dc7:
#> [1] 1 3
#>

chvatal <- make_graph("chvatal")
min_st_separators(chvatal)
#> [[1]]
#> + 4/12 vertices, from a079300:
#> [1]  7 10 11 12
#>
#> [[2]]
#> + 4/12 vertices, from a079300:
#> [1]  3  6  8 11
#>
#> [[3]]
#> + 4/12 vertices, from a079300:
#> [1]  2  7  9 12
#>
#> [[4]]
#> + 4/12 vertices, from a079300:
#> [1]  8 10 11 12
#>
#> [[5]]
#> + 4/12 vertices, from a079300:
#> [1]  6  9 11 12
#>
#> [[6]]
#> + 4/12 vertices, from a079300:
#> [1]  2  5  7 10
#>
#> [[7]]
#> + 4/12 vertices, from a079300:
#> [1] 1 3 6 8
#>
#> [[8]]
#> + 4/12 vertices, from a079300:
#> [1] 2 4 7 9
#>
#> [[9]]
#> + 4/12 vertices, from a079300:
#> [1]  3  5  8 10
#>
#> [[10]]
#> + 4/12 vertices, from a079300:
#> [1] 1 4 6 9
#>
#> [[11]]
#> + 4/12 vertices, from a079300:
#> [1] 1 2 4 5
#>
#> [[12]]
#> + 4/12 vertices, from a079300:
#> [1] 1 3 4 5
#>
#> [[13]]
#> + 6/12 vertices, from a079300:
#> [1]  3  6  8 10 11 12
#>
#> [[14]]
#> + 6/12 vertices, from a079300:
#> [1]  4  6  7  9 11 12
#>
#> [[15]]
#> + 6/12 vertices, from a079300:
#> [1]  2  4  5  7 10 12
#>
#> [[16]]
#> + 6/12 vertices, from a079300:
#> [1]  3  4  5  7 10 11
#>
#> [[17]]
#> + 6/12 vertices, from a079300:
#> [1]  6  7  8  9 11 12
#>
#> [[18]]
#> + 6/12 vertices, from a079300:
#> [1]  3  5  7  8 10 11
#>
#> [[19]]
#> + 6/12 vertices, from a079300:
#> [1]  3  4  6  7  9 11
#>
#> [[20]]
#> + 6/12 vertices, from a079300:
#> [1] 1 3 4 5 6 8
#>
#> [[21]]
#> + 6/12 vertices, from a079300:
#> [1]  1  2  6  8  9 12
#>
#> [[22]]
#> + 6/12 vertices, from a079300:
#> [1]  2  5  7  8 10 12
#>
#> [[23]]
#> + 6/12 vertices, from a079300:
#> [1] 1 2 4 5 7 9
#>
#> [[24]]
#> + 6/12 vertices, from a079300:
#> [1]  2  7  9 10 11 12
#>
#> [[25]]
#> + 6/12 vertices, from a079300:
#> [1]  1  6  8  9 11 12
#>
#> [[26]]
#> + 6/12 vertices, from a079300:
#> [1]  1  2  5  8 10 12
#>
#> [[27]]
#> + 6/12 vertices, from a079300:
#> [1]  1  3  5  8 10 11
#>
#> [[28]]
#> + 6/12 vertices, from a079300:
#> [1]  1  2  4  6  9 12
#>
#> [[29]]
#> + 6/12 vertices, from a079300:
#> [1]  1  3  4  6  9 11
#>
#> [[30]]
#> + 6/12 vertices, from a079300:
#> [1]  1  2  3  5  8 10
#>
#> [[31]]
#> + 6/12 vertices, from a079300:
#> [1] 1 2 3 4 6 9
#>
#> [[32]]
#> + 6/12 vertices, from a079300:
#> [1]  2  3  4  5  7 10
#>