88 lines
1.6 KiB
Go
88 lines
1.6 KiB
Go
package dag
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import (
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"sync"
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)
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// Set is a set data structure.
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type Set struct {
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m map[interface{}]interface{}
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once sync.Once
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}
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// Hashable is the interface used by set to get the hash code of a value.
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// If this isn't given, then the value of the item being added to the set
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// itself is used as the comparison value.
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type Hashable interface {
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Hashcode() interface{}
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}
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// hashcode returns the hashcode used for set elements.
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func hashcode(v interface{}) interface{} {
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if h, ok := v.(Hashable); ok {
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return h.Hashcode()
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}
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return v
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}
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// Add adds an item to the set
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func (s *Set) Add(v interface{}) {
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s.once.Do(s.init)
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s.m[hashcode(v)] = v
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}
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// Delete removes an item from the set.
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func (s *Set) Delete(v interface{}) {
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s.once.Do(s.init)
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delete(s.m, hashcode(v))
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}
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// Include returns true/false of whether a value is in the set.
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func (s *Set) Include(v interface{}) bool {
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s.once.Do(s.init)
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_, ok := s.m[hashcode(v)]
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return ok
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}
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// Intersection computes the set intersection with other.
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func (s *Set) Intersection(other *Set) *Set {
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result := new(Set)
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if other != nil {
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for _, v := range s.m {
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if other.Include(v) {
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result.Add(v)
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}
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}
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}
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return result
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}
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// Len is the number of items in the set.
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func (s *Set) Len() int {
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if s == nil {
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return 0
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}
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return len(s.m)
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}
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// List returns the list of set elements.
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func (s *Set) List() []interface{} {
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if s == nil {
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return nil
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}
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r := make([]interface{}, 0, len(s.m))
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for _, v := range s.m {
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r = append(r, v)
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}
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return r
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}
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func (s *Set) init() {
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s.m = make(map[interface{}]interface{})
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}
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