delaunay/mst working

util/uf/uf.go

@@ -0,0 +1,72 @@
+package uf
+
+import "fmt"
+
+// Interface is how you use the union-find data structure.
+type Interface interface {
+	Find(p int) int
+	Count() int
+	Connected(p, q int) bool
+	Union(p, q int)
+	validate(p int)
+}
+
+type instance struct {
+	parent []int
+	rank   []byte
+	count  int
+}
+
+func (i *instance) Find(p int) int {
+	i.validate(p)
+	for p != i.parent[p] {
+		i.parent[p] = i.parent[i.parent[p]]
+		p = i.parent[p]
+	}
+	return p
+}
+
+func (i *instance) Count() int {
+	return i.count
+}
+
+func (i *instance) Connected(p, q int) bool {
+	return i.Find(p) == i.Find(q)
+}
+
+func (i *instance) Union(p, q int) {
+	rootP := i.Find(p)
+	rootQ := i.Find(q)
+	if rootP == rootQ {
+		return
+	}
+	switch {
+	case i.rank[rootP] < i.rank[rootQ]:
+		i.parent[rootP] = rootQ
+	case i.rank[rootP] > i.rank[rootQ]:
+		i.parent[rootQ] = rootP
+	default:
+		i.parent[rootQ] = rootP
+		i.rank[rootP]++
+	}
+	i.count--
+}
+
+func (i *instance) validate(p int) {
+	if n := len(i.parent); p < 0 || p >= n {
+		panic(fmt.Sprintf("index %d is not between 0 and %d", p, n-1))
+	}
+}
+
+// New creates a new instance of a union-find interface.
+func New(n int) Interface {
+	created := &instance{
+		parent: make([]int, n),
+		rank:   make([]byte, n),
+		count:  n,
+	}
+	for i := 0; i < n; i++ {
+		created.parent[i] = i
+	}
+	return created
+}