Use this if you are using igraph from R
The girth of a graph is the length of the shortest circle in it.
girth(graph, circle = TRUE)
graph |
The input graph. It may be directed, but the algorithm searches for undirected circles anyway. |
circle |
Logical scalar, whether to return the shortest circle itself. |
The current implementation works for undirected graphs only, directed graphs are treated as undirected graphs. Loop edges and multiple edges are ignored. If the graph is a forest (ie. acyclic), then zero is returned.
This implementation is based on Alon Itai and Michael Rodeh: Finding a minimum circuit in a graph Proceedings of the ninth annual ACM symposium on Theory of computing, 1-10, 1977. The first implementation of this function was done by Keith Briggs, thanks Keith.
A named list with two components:
girth |
Integer constant, the girth of the graph, or 0 if the graph is acyclic. |
circle |
Numeric vector with the vertex ids in the shortest circle. |
Gabor Csardi csardi.gabor@gmail.com
Alon Itai and Michael Rodeh: Finding a minimum circuit in a graph Proceedings of the ninth annual ACM symposium on Theory of computing, 1-10, 1977
# No circle in a tree g <- make_tree(1000, 3) girth(g) # The worst case running time is for a ring g <- make_ring(100) girth(g) # What about a random graph? g <- sample_gnp(1000, 1/1000) girth(g)