public void Smoke_Test_DisJointSet()
{
var disjointSet = new DisJointSet <int>();
for (int i = 1; i <= 7; i++)
{
disjointSet.MakeSet(i);
}
disjointSet.Union(1, 2);
Assert.AreEqual(1, disjointSet.FindSet(2));
disjointSet.Union(2, 3);
Assert.AreEqual(1, disjointSet.FindSet(3));
disjointSet.Union(4, 5);
Assert.AreEqual(4, disjointSet.FindSet(4));
disjointSet.Union(5, 6);
Assert.AreEqual(4, disjointSet.FindSet(5));
disjointSet.Union(6, 7);
Assert.AreEqual(4, disjointSet.FindSet(6));
Assert.AreEqual(4, disjointSet.FindSet(4));
disjointSet.Union(3, 4);
Assert.AreEqual(1, disjointSet.FindSet(4));
}
FindMinimumSpanningTree(WeightedGraph <T, W> graph)
{
var edges = new List <MSTEdge <T, W> >();
//gather all unique edges
DFS(graph.ReferenceVertex, new HashSet <T>(),
new Dictionary <T, HashSet <T> >(),
edges);
//quick sort preparation
var sortArray = new MSTEdge <T, W> [edges.Count];
for (int i = 0; i < edges.Count; i++)
{
sortArray[i] = edges[i];
}
//quick sort edges
var sortedEdges = MergeSort <MSTEdge <T, W> > .Sort(sortArray);
var result = new List <MSTEdge <T, W> >();
var disJointSet = new DisJointSet <T>();
//create set
foreach (var vertex in graph.Vertices)
{
disJointSet.MakeSet(vertex.Key);
}
//pick each edge one by one
//if both source & target belongs to same set
//then don't add the edge to result
//otherwise add it to result and union sets
for (int i = 0; i < edges.Count; i++)
{
var currentEdge = sortedEdges[i];
var setA = disJointSet.FindSet(currentEdge.Source);
var setB = disJointSet.FindSet(currentEdge.Destination);
//can't pick edge with both ends already in MST
if (setA.Equals(setB))
{
continue;
}
result.Add(currentEdge);
//union picked edge vertice sets
disJointSet.Union(setA, setB);
}
return(result);
}
public int MinMalwareSpread(int[][] graph, int[] initial)
{
var ds = new DisJointSet(graph.Length);
for (int i = 0; i < graph.Length; i++)
{
for (int j = i + 1; j < graph.Length; j++)
{
if (graph[i][j] == 1)
{
ds.Union(i, j);
}
}
}
var Count = new int[graph.Length];
foreach (var node in initial)
{
Count[ds.Find(node)]++;
}
int ans = -1, ansSize = -1;
foreach (var node in initial)
{
int root = ds.Find(node);
if (Count[root] == 1)
{
int curSize = ds.Size(root);
if (curSize > ansSize || (curSize == ansSize && node < ans))
{
ans = node;
ansSize = curSize;
}
}
}
if (ans == -1)
{
ans = Int16.MaxValue;
foreach (var node in initial)
{
ans = Math.Min(ans, node);
}
}
return(ans);
}
