public long[] CalcShortestPathsByHeap(EdgeEndPoint[][] adjacencyList, int v)
{
var vertices = adjacencyList
.Select(p => new VertexInfo {
Path = long.MaxValue, Adjacents = p
})
.ToArray();
vertices[v].Path = 0;
var front = new GenericBinaryHeap <VertexInfo>(
(x, y) => x.Path.CompareTo(y.Path),
(vi, i) => vi.IndexInHeap = i);
front.Insert(vertices[v]);
while (front.Count > 0)
{
var u = front.Min;
front.DeleteMin();
if (u.Visited)
{
continue;
}
u.Visited = true;
foreach (var edge in u.Adjacents)
{
var to = vertices[edge.To];
if (to.Visited)
{
continue;
}
var w = u.Path + edge.Weight;
if (w < to.Path)
{
if (front.Count > 0 && front[to.IndexInHeap] == to)
{
front.Remove(to.IndexInHeap);
}
to.Path = w;
}
front.Insert(to);
}
}
return(vertices.Select(vi => vi.Path).ToArray());
}
public List <Edge> Prim(List <Edge>[] graph)
{
// O(m * log n), m edges, n vertices
var mst = new List <Edge>();
var start = new Random().Next(graph.Length - 1) + 1;
var visited = new bool[graph.Length];
visited[start] = true;
var heap = new GenericBinaryHeap <VertexInfo>(
(x, y) => x.Cost.CompareTo(y.Cost),
(info, index) => info.IndexInHeap = index);
var infos = new VertexInfo[graph.Length];
for (var i = 0; i < infos.Length; i++)
{
if (graph[i] != null && i != start)
{
infos[i] = new VertexInfo {
Cost = long.MaxValue
}
}
}
;
heap.FillRaw(infos.Where(i => i != null));
foreach (var edge in graph[start])
{
var vertexInfo = infos[edge.To];
vertexInfo.KeyEdge = edge;
vertexInfo.Cost = edge.Weight;
heap.BubbleUp(vertexInfo.IndexInHeap);
}
while (heap.Count > 0)
{
var uv = heap.Min.KeyEdge;
mst.Add(uv);
heap.DeleteMin();
visited[uv.To] = true;
foreach (var edge in graph[uv.To])
{
if (!visited[edge.To])
{
var info = infos[edge.To];
if (edge.Weight < info.Cost)
{
info.Cost = edge.Weight;
info.KeyEdge = edge;
heap.BubbleUp(info.IndexInHeap);
}
}
}
}
return(mst);
}
