Function vertex_connectivity 

pub fn vertex_connectivity(graph: &Graph, checks: bool) -> IgraphResult<i64>

Vertex connectivity (cohesion) of a graph.

Returns the minimum number of internal vertices that must be removed to disconnect some pair of vertices in graph. Equal to min_{s ≠ t} st_vertex_connectivity(s, t, VconnNei::NumberOfNodes).

Counterpart of igraph_vertex_connectivity (references/igraph/src/flow/flow.c:2158) and its alias igraph_cohesion (flow.c:2470).

Arguments

• graph — input graph (directed or undirected).
• checks — when true, run the cheap short-circuits described in the module docs before falling back to the O(V^2) pairwise loop. Recommended for any non-trivial graph; the helpers cost O(V + E) and can replace the whole pairwise loop. Equivalent to igraph C’s checks argument.

Returns

The vertex connectivity as i64. Returns:

• 0 when vcount() < 2, or the graph is disconnected (some pair is already separated).
• 1 when there is a vertex with degree 1 (undirected) or min(in, out) = 1 (directed).
• vcount - 1 when the graph is complete.
• Otherwise, the result of the pairwise FL-013 loop.

Errors

Propagates errors from st_vertex_connectivity, connected_components, strongly_connected_components, and is_complete. In practice these arise only from arithmetic overflow on very large graphs, which is unreachable here.

Examples

use rust_igraph::{Graph, vertex_connectivity};

// Undirected ring on 5 vertices — vc = 2 (any single vertex
// removal leaves the rest connected).
let mut g = Graph::new(5, false).unwrap();
for (u, v) in [(0u32, 1u32), (1, 2), (2, 3), (3, 4), (4, 0)] {
    g.add_edge(u, v).unwrap();
}
assert_eq!(vertex_connectivity(&g, true).unwrap(), 2);

// Undirected path on 5 vertices — vc = 1 (the two endpoints
// each have degree 1).
let mut p = Graph::new(5, false).unwrap();
for (u, v) in [(0u32, 1u32), (1, 2), (2, 3), (3, 4)] {
    p.add_edge(u, v).unwrap();
}
assert_eq!(vertex_connectivity(&p, true).unwrap(), 1);