Function is_chordal 

pub fn is_chordal(
    graph: &Graph,
    alpha: Option<&[u32]>,
) -> IgraphResult<ChordalResult>

Tests whether a graph is chordal.

A graph is chordal if every cycle of four or more nodes has a chord (an edge joining two non-adjacent nodes in the cycle). Equivalently, all chordless cycles have at most three nodes.

Uses the MCS ordering from maximum_cardinality_search and the zero-fill-in test of Tarjan-Yannakakis 1984. Optionally computes the fill-in edges needed to make the graph chordal (note: the fill-in is not guaranteed to be minimal).

Edge directions are ignored. Self-loops and multi-edges are stripped internally.

Arguments

• graph — the input graph.
• alpha — optional pre-computed MCS ordering (alpha[v] = rank). If None, MCS is computed internally.

Returns

A ChordalResult with chordal flag and fill_in edges.

Complexity

O(|V| + |E|).

Examples

use rust_igraph::{is_chordal, create};

// Triangle is chordal
let g = create(&[(0, 1), (1, 2), (2, 0)], 3, false).unwrap();
let r = is_chordal(&g, None).unwrap();
assert!(r.chordal);
assert!(r.fill_in.is_empty());

// 4-cycle is not chordal (needs one diagonal)
let g4 = create(&[(0, 1), (1, 2), (2, 3), (3, 0)], 4, false).unwrap();
let r4 = is_chordal(&g4, None).unwrap();
assert!(!r4.chordal);
assert!(!r4.fill_in.is_empty());