/
set.go
282 lines (256 loc) · 5.16 KB
/
set.go
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// The set package implements efficient integer sets
package set
import (
"fmt"
"rand"
)
// IntSet provides an interface for general integer set operations.
type IntSet interface {
// Initialize the set with elements from an array slice.
// Duplicates are ignored, of course.
Init(a []int) *IntSet
// Insert a new element into the set.
// Non-destructive at the moment.
Insert(x int) *IntSet
// Tests whether the given element is contained in the set.
Elem(x int) bool
// Takes the union of the two sets, non-destructive.
Union(y IntSet) *IntSet
// Union (parallel version!)
UnionPar(y IntSet) *IntSet
// Takes the intersection of the two sets, non-destructive.
Intersection(y *IntSet) *IntSet
// Takes the set difference of the two sets.
Diff(y *IntSet) *IntSet
// remove me
Display()
}
type IntTreap struct {
x int // value
p int // randomized priority
left *IntTreap // left subtreap
right *IntTreap // right subtreap
}
func Init(a []int) *IntTreap {
var s *IntTreap = nil
for i := 0; i < len(a); i++ {
s = s.Insert(a[i])
}
return s
}
func (s *IntTreap) Insert(x int) *IntTreap {
if (s == nil) {
s := new(IntTreap)
s.x = x
s.p = rand.Int()
s.left = nil
s.right = nil
return s
}
if (s.x == x) {
return s
} else if (s.x > x) {
if s.left != nil {
s.left = s.left.Insert(x)
} else {
s.left = NewIntTreap()
s.left.x = x
s.left.p = rand.Int()
s.left.left = nil
s.left.right = nil
}
if s.left.p > s.p {
return RightSwap(s.left, s)
} else {
return s
}
} else if (s.x < x) {
if s.right != nil {
s.right = s.right.Insert(x)
} else {
s.right = NewIntTreap()
s.right.x = x
s.right.p = rand.Int()
s.right.left = nil
s.right.right = nil
}
if s.right.p > s.p {
return LeftSwap(s.right, s)
} else {
return s
}
}
return nil
}
func (s *IntTreap) Elem(x int) bool {
if (s == nil) {
return false
}
if (s.x == x) {
return true
} else if (s.x > x) {
if (s.left == nil) {
return false
}
return s.left.Elem(x)
} else {
if (s.right == nil) {
return false
}
return s.right.Elem(x)
}
return false
}
/* RightSwap
* When the pivot is to the left of the root, do a left tree rotation
*/
func RightSwap(pivot *IntTreap, root *IntTreap) *IntTreap {
root.left = pivot.right
pivot.right = root
return pivot
}
/* LeftSwap
* When the pivot is to the right of the root, do a right tree rotation
*/
func LeftSwap(pivot *IntTreap, root *IntTreap) *IntTreap {
root.right = pivot.left
pivot.left = root
return pivot
}
/* Split
* Split the treap by a key k, the left tree is all keys < k,
* the right tree is all keys > k
*/
func (s *IntTreap) Split(k int) (*IntTreap, int, *IntTreap) {
if (s == nil) {
return nil, 0, nil
}
if (k == s.x) {
return s.left, s.x, s.right
}
if (k < s.x) {
Tl, m, T2 := s.left.Split(k)
Tr := NewIntTreap()
Tr.left = T2
Tr.x = s.x
Tr.p = s.p
Tr.right = s.right
return Tl, m, Tr
}
if (k > s.x) {
T2, m, Tr := s.right.Split(k)
Tl := NewIntTreap()
Tl.left = s.left
Tl.x = s.x
Tl.p = s.p
Tl.right = T2
return Tl, m, Tr
}
return nil, 0, nil
}
func (s *IntTreap) Join(t *IntTreap) *IntTreap {
if (s == nil) {
return t
} else if (t == nil) {
return s
} else if (s.p > t.p) {
tr := s.right.Join(t)
tnew := NewIntTreap()
tnew.left = s.left
tnew.x = s.x
tnew.p = s.p
tnew.right = tr
return tnew
} else {
tl := s.Join(t.left)
tnew := NewIntTreap()
tnew.left = tl
tnew.x = t.x
tnew.p = t.p
tnew.right = t.right
return tnew
}
return nil
}
/* Union
* Takes the union of s and t
* Destructive?
*/
func (s *IntTreap) Union(t *IntTreap) *IntTreap {
u := new(IntTreap)
if (s == nil) { return t }
if (t == nil) { return s }
if (s.p < t.p) {
temp := t
t = s
s = temp
}
Tl, _, Tr := t.Split(s.x)
u.x = s.x
u.p = s.p
u.left = s.left.Union(Tl)
u.right = s.right.Union(Tr)
return u
}
// broken goroutine version
func (s *IntTreap) UnionPar(t *IntTreap) *IntTreap {
ch := make(chan *IntTreap)
if (s == nil) { return t }
if (t == nil) { return s }
go s.UnionHelper(t, ch)
u := <- ch
return u
}
func (s *IntTreap) UnionHelper(t *IntTreap, ch chan *IntTreap) {
u := new(IntTreap)
if (s == nil) {
ch <- t
} else if (t == nil) {
ch <- s
} else if (s.p >= t.p) {
Tl, _, Tr := t.Split(s.x)
u.x = s.x
u.p = s.p
// chl := make(chan *IntTreap)
// chr := make(chan *IntTreap)
// go s.left.UnionHelper(Tl, chl)
// go s.right.UnionHelper(Tr, chr)
// u.left = <-chl
// u.right = <-chr
u.left = s.left.Union(Tl)
u.right = s.right.Union(Tr)
ch <- u
} else {
Sl, _, Sr := s.Split(t.x)
u.x = t.x
u.p = t.p
// chl := make(chan *IntTreap)
// chr := make(chan *IntTreap)
// go t.left.UnionHelper(Sl, chl)
// go t.right.UnionHelper(Sr, chr)
// u.left = <-chl
// u.right = <-chr
u.left = s.left.Union(Sl)
u.right = s.right.Union(Sr)
ch <- u
}
}
func NewIntTreap() *IntTreap {
return new(IntTreap)
}
func NewIntLeaf(x int) *IntTreap {
l := new(IntTreap)
l.x = x
l.p = rand.Int()
l.left = nil
l.right = nil
return l
}
// debugging, remove after
func (s *IntTreap) Display() {
if s != nil {
s.left.Display()
fmt.Printf("%d ", s.x)
s.right.Display()
}
}