Function bellman_ford_distances 

pub fn bellman_ford_distances(
    graph: &Graph,
    source: VertexId,
    weights: &[f64],
) -> IgraphResult<Vec<Option<f64>>>

Single-source Bellman-Ford shortest distances on graph from source, following out-edges on directed graphs.

Returns distances[v]: Some(d) if v is reachable from source, None otherwise. distances[source] == Some(0.0).

weights[e] is the weight of edge e; length must equal graph.ecount(). Negative weights are allowed; NaN weights are rejected (IgraphError::InvalidArgument). If a negative cycle is reachable from the source, returns IgraphError::InvalidArgument with a “negative cycle” message (matches upstream’s IGRAPH_ENEGCYCLE semantics).

Use this instead of crate::dijkstra_distances when edge weights can be negative. For non-negative weights Dijkstra is asymptotically faster (O((V+E) log V) vs Bellman-Ford’s O(V·E)).

Counterpart of igraph_distances_bellman_ford(_, _, vss(source), vss_all(), weights, IGRAPH_OUT).

Examples

use rust_igraph::{Graph, bellman_ford_distances};

// Directed graph 0 → 1 → 2 with weights 3, -1 — Bellman-Ford
// handles the negative edge that would break Dijkstra's
// monotonicity assumption.
let mut g = Graph::new(3, true).unwrap();
g.add_edge(0, 1).unwrap();  // edge 0, weight 3
g.add_edge(1, 2).unwrap();  // edge 1, weight -1
let d = bellman_ford_distances(&g, 0, &[3.0, -1.0]).unwrap();
assert_eq!(d, vec![Some(0.0), Some(3.0), Some(2.0)]);