public int MinCostConnectPoints(int[][] points)
{
var n = points.Length;
var l = new List <Edge>(n * n);
for (var i = 0; i < n - 1; i++)
{
for (var j = i + 1; j < n; j++)
{
var length = Math.Abs(points[i][0] - points[j][0]) + Math.Abs(points[i][1] - points[j][1]);
l.Add(new Edge(i, j, length));
}
}
var orderList = l.OrderBy(i => i.Length);
var res = 0;
var uf = new UF(n);
foreach (var listItem in orderList)
{
var fx = uf.Find(listItem.X);
var fy = uf.Find(listItem.Y);
if (fx != fy)
{
res += listItem.Length;
uf.Union(fx, fy);
}
}
return(res);
}
private readonly double _weight; // weight of MST
/// <summary>
/// Compute a minimum spanning tree (or forest) of an edge-weighted graph.
/// </summary>
/// <param name="g">g the edge-weighted graph</param>
public BoruvkaMST(EdgeWeightedGraph g)
{
var uf = new UF(g.V);
// repeat at most log V times or until we have V-1 edges
for (var t = 1; t < g.V && _mst.Size() < g.V - 1; t = t + t)
{
// foreach tree in forest, find closest edge
// if edge weights are equal, ties are broken in favor of first edge in G.edges()
var closest = new EdgeW[g.V];
foreach (var e in g.Edges())
{
int v = e.Either(), w = e.Other(v);
int i = uf.Find(v), j = uf.Find(w);
if (i == j)
{
continue; // same tree
}
if (closest[i] == null || Less(e, closest[i]))
{
closest[i] = e;
}
if (closest[j] == null || Less(e, closest[j]))
{
closest[j] = e;
}
}
// add newly discovered edges to MST
for (var i = 0; i < g.V; i++)
{
var e = closest[i];
if (e != null)
{
int v = e.Either(), w = e.Other(v);
// don't add the same edge twice
if (!uf.Connected(v, w))
{
_mst.Add(e);
_weight += e.Weight;
uf.Union(v, w);
}
}
}
}
// check optimality conditions
//assert check(G);
}
