Function st_vertex_connectivity 

pub fn st_vertex_connectivity(
    graph: &Graph,
    source: VertexId,
    target: VertexId,
    mode: VconnNei,
) -> IgraphResult<i64>

Vertex connectivity between two vertices.

Counterpart of igraph_st_vertex_connectivity in references/igraph/src/flow/flow.c:1922. Returns the minimum number of internal vertices whose removal disconnects source from target.

Arguments

• graph — input graph (directed or undirected). Undirected input is treated as if every edge is two anti-parallel directed arcs (IGRAPH_TO_DIRECTED_MUTUAL), matching igraph C.
• source — source vertex id (0 ≤ source < vcount()).
• target — target vertex id (0 ≤ target < vcount(), target != source).
• mode — how to handle a direct source → target edge. See VconnNei.

Returns

The s-t vertex connectivity as i64. Returns 0 when source and target are in disjoint components. When mode is VconnNei::Negative and a direct edge exists, returns -1.

Errors

• IgraphError::InvalidArgument if source == target, vcount() < 2, or mode == VconnNei::Error and a direct edge source → target exists.
• IgraphError::VertexOutOfRange if source or target is outside [0, vcount()).
• IgraphError::Internal if the unit-capacity max-flow value is not representable as i64 (unreachable in practice: the value is bounded above by vcount()).

Examples

use rust_igraph::{Graph, VconnNei, st_vertex_connectivity};

// Path 0 — 1 — 2 — 3 — 4 — 5 (undirected). Any single internal
// vertex separates endpoints → s-t vertex connectivity = 1.
let mut g = Graph::new(6, false).unwrap();
for (u, v) in [(0, 1), (1, 2), (2, 3), (3, 4), (4, 5)] {
    g.add_edge(u, v).unwrap();
}
assert_eq!(
    st_vertex_connectivity(&g, 0, 5, VconnNei::Error).unwrap(),
    1
);