public static int ComputeMinSpanningTreeCost(string path)
{
IUndirectedWeightedGraph <int> graph = ParseGraph(path);
var result = Foo(graph);
return(42);
}
private static int Foo(IUndirectedWeightedGraph <int> graph)
{
List <int> vertices = graph.GetVertices().ToList();
var x = new List <int> {
vertices.First()
};
// consider data structure for t
var t = new List <int>(); // Invariant: X = vertices spanned by tree-so-far T
var result = 0;
while (x.Count != vertices.Count)
{
// let e = (u, v) be the cheapest edge of G with u belongs X, v do not belongs X
var cheapestScores = new List <(int vertex, int score)>();
foreach (int u in x)
{
(int v, int weight) = graph.GetAdjacentVertices(u)
.Where(i => !x.Contains(i.w)) // expensive contains
.OrderBy(edge => edge.weight)
.First();
cheapestScores.Add((v, weight)); // maybe better solution?
}
// var zzz = graph.GetAdjacentVertices(u)
// .Where(i => !x.Contains(i.w)).ToList()
// .OrderBy(edge => edge.weight)
// .First();
var cheapestPath = cheapestScores.OrderBy(tuple => tuple.score)
.First(); // min instead of OrderBy?
// add e to T
t.Add(cheapestPath.score);
// add v to X
x.Add(cheapestPath.vertex);
result += cheapestPath.score;
}
return(result);
}
