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155 lines
3.7 KiB
Go
155 lines
3.7 KiB
Go
// Copyright (c) 2015, Emir Pasic. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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// Package hashset implements a set backed by a hash table.
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//
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// Structure is not thread safe.
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//
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// References: http://en.wikipedia.org/wiki/Set_%28abstract_data_type%29
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package hashset
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import (
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"fmt"
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"strings"
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"github.com/emirpasic/gods/v2/sets"
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)
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// Assert Set implementation
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var _ sets.Set[int] = (*Set[int])(nil)
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// Set holds elements in go's native map
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type Set[T comparable] struct {
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items map[T]struct{}
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}
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var itemExists = struct{}{}
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// New instantiates a new empty set and adds the passed values, if any, to the set
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func New[T comparable](values ...T) *Set[T] {
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set := &Set[T]{items: make(map[T]struct{})}
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if len(values) > 0 {
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set.Add(values...)
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}
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return set
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}
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// Add adds the items (one or more) to the set.
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func (set *Set[T]) Add(items ...T) {
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for _, item := range items {
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set.items[item] = itemExists
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}
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}
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// Remove removes the items (one or more) from the set.
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func (set *Set[T]) Remove(items ...T) {
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for _, item := range items {
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delete(set.items, item)
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}
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}
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// Contains check if items (one or more) are present in the set.
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// All items have to be present in the set for the method to return true.
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// Returns true if no arguments are passed at all, i.e. set is always superset of empty set.
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func (set *Set[T]) Contains(items ...T) bool {
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for _, item := range items {
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if _, contains := set.items[item]; !contains {
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return false
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}
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}
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return true
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}
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// Empty returns true if set does not contain any elements.
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func (set *Set[T]) Empty() bool {
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return set.Size() == 0
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}
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// Size returns number of elements within the set.
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func (set *Set[T]) Size() int {
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return len(set.items)
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}
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// Clear clears all values in the set.
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func (set *Set[T]) Clear() {
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set.items = make(map[T]struct{})
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}
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// Values returns all items in the set.
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func (set *Set[T]) Values() []T {
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values := make([]T, set.Size())
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count := 0
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for item := range set.items {
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values[count] = item
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count++
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}
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return values
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}
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// String returns a string representation of container
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func (set *Set[T]) String() string {
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str := "HashSet\n"
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items := []string{}
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for k := range set.items {
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items = append(items, fmt.Sprintf("%v", k))
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}
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str += strings.Join(items, ", ")
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return str
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}
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// Intersection returns the intersection between two sets.
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// The new set consists of all elements that are both in "set" and "another".
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// Ref: https://en.wikipedia.org/wiki/Intersection_(set_theory)
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func (set *Set[T]) Intersection(another *Set[T]) *Set[T] {
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result := New[T]()
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// Iterate over smaller set (optimization)
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if set.Size() <= another.Size() {
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for item := range set.items {
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if _, contains := another.items[item]; contains {
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result.Add(item)
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}
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}
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} else {
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for item := range another.items {
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if _, contains := set.items[item]; contains {
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result.Add(item)
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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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// Union returns the union of two sets.
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// The new set consists of all elements that are in "set" or "another" (possibly both).
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// Ref: https://en.wikipedia.org/wiki/Union_(set_theory)
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func (set *Set[T]) Union(another *Set[T]) *Set[T] {
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result := New[T]()
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for item := range set.items {
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result.Add(item)
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}
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for item := range another.items {
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result.Add(item)
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}
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return result
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}
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// Difference returns the difference between two sets.
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// The new set consists of all elements that are in "set" but not in "another".
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// Ref: https://proofwiki.org/wiki/Definition:Set_Difference
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func (set *Set[T]) Difference(another *Set[T]) *Set[T] {
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result := New[T]()
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for item := range set.items {
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if _, contains := another.items[item]; !contains {
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result.Add(item)
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}
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}
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return result
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}
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