Function dijkstra 

pub fn dijkstra(
    graph: &Graph,
    start_node: usize,
) -> (Vec<f64>, Vec<Option<usize>>)

Finds the shortest paths from a single source node to all other nodes using Dijkstra’s algorithm.

Dijkstra’s algorithm is a greedy algorithm that solves the single-source shortest path problem for a graph with non-negative edge weights.

Arguments

• graph - The graph to search.
• start_node - The index of the starting node.

Returns

A tuple containing:

• A vector of distances from the start node to each node.
• A vector of predecessors to reconstruct the shortest paths.