github.com/songzhibin97/go-baseutils@v0.0.2-0.20240302024150-487d8ce9c082/structure/sets/treeset/treeset.go

// Package treeset implements a tree backed by a red-black tree.
//
// Structure is not thread safe.
//
// Reference: http://en.wikipedia.org/wiki/Set_%28abstract_data_type%29
package treeset

import (
	"encoding/json"
	"fmt"
	"reflect"
	"strings"

	"github.com/songzhibin97/go-baseutils/base/bcomparator"
	"github.com/songzhibin97/go-baseutils/structure/sets"
	"github.com/songzhibin97/go-baseutils/structure/trees/redblacktree"
)

var _ sets.Set[any] = (*Set[any])(nil)

// Set holds elements in a red-black tree
type Set[E any] struct {
	tree *redblacktree.Tree[E, struct{}]
	zero E
}

var itemExists = struct{}{}

// NewWith instantiates a new empty set with the custom comparator.
func NewWith[E any](comparator bcomparator.Comparator[E], values ...E) *Set[E] {
	set := &Set[E]{tree: redblacktree.NewWith[E, struct{}](comparator)}
	if len(values) > 0 {
		set.Add(values...)
	}
	return set
}

// NewWithIntComparator instantiates a new empty set with the IntComparator, i.e. keys are of type int.
func NewWithIntComparator(values ...int) *Set[int] {
	set := &Set[int]{tree: redblacktree.NewWithIntComparator[struct{}]()}
	if len(values) > 0 {
		set.Add(values...)
	}
	return set
}

// NewWithStringComparator instantiates a new empty set with the StringComparator, i.e. keys are of type string.
func NewWithStringComparator(values ...string) *Set[string] {
	set := &Set[string]{tree: redblacktree.NewWithStringComparator[struct{}]()}
	if len(values) > 0 {
		set.Add(values...)
	}
	return set
}

// Add adds the items (one or more) to the set.
func (set *Set[E]) Add(items ...E) {
	for _, item := range items {
		set.tree.Put(item, itemExists)
	}
}

// Remove removes the items (one or more) from the set.
func (set *Set[E]) Remove(items ...E) {
	for _, item := range items {
		set.tree.Remove(item)
	}
}

// Contains checks weather items (one or more) are present in the set.
// All items have to be present in the set for the method to return true.
// Returns true if no arguments are passed at all, i.e. set is always superset of empty set.
func (set *Set[E]) Contains(items ...E) bool {
	for _, item := range items {
		if _, contains := set.tree.Get(item); !contains {
			return false
		}
	}
	return true
}

// Empty returns true if set does not contain any elements.
func (set *Set[E]) Empty() bool {
	return set.tree.Size() == 0
}

// Size returns number of elements within the set.
func (set *Set[E]) Size() int {
	return set.tree.Size()
}

// Clear clears all values in the set.
func (set *Set[E]) Clear() {
	set.tree.Clear()
}

// Values returns all items in the set.
func (set *Set[E]) Values() []E {
	return set.tree.Keys()
}

// String returns a string representation of container
func (set *Set[E]) String() string {
	b := strings.Builder{}
	b.WriteString("TreeSet\n")
	for _, v := range set.tree.Keys() {
		b.WriteString(fmt.Sprintf("(key:%v) ", v))
	}
	return b.String()
}

// Intersection returns the intersection between two sets.
// The new set consists of all elements that are both in "set" and "another".
// The two sets should have the same comparators, otherwise the result is empty set.
// Ref: https://en.wikipedia.org/wiki/Intersection_(set_theory)
func (set *Set[E]) Intersection(another *Set[E]) *Set[E] {
	result := NewWith(set.tree.Comparator)

	setComparator := reflect.ValueOf(set.tree.Comparator)
	anotherComparator := reflect.ValueOf(another.tree.Comparator)
	if setComparator.Pointer() != anotherComparator.Pointer() {
		return result
	}

	// Iterate over smaller set (optimization)
	if set.Size() <= another.Size() {
		for it := set.Iterator(); it.Next(); {
			if another.Contains(it.Value()) {
				result.Add(it.Value())
			}
		}
	} else {
		for it := another.Iterator(); it.Next(); {
			if set.Contains(it.Value()) {
				result.Add(it.Value())
			}
		}
	}

	return result
}

// Union returns the union of two sets.
// The new set consists of all elements that are in "set" or "another" (possibly both).
// The two sets should have the same comparators, otherwise the result is empty set.
// Ref: https://en.wikipedia.org/wiki/Union_(set_theory)
func (set *Set[E]) Union(another *Set[E]) *Set[E] {
	result := NewWith(set.tree.Comparator)

	setComparator := reflect.ValueOf(set.tree.Comparator)
	anotherComparator := reflect.ValueOf(another.tree.Comparator)
	if setComparator.Pointer() != anotherComparator.Pointer() {
		return result
	}

	for it := set.Iterator(); it.Next(); {
		result.Add(it.Value())
	}
	for it := another.Iterator(); it.Next(); {
		result.Add(it.Value())
	}

	return result
}

// Difference returns the difference between two sets.
// The two sets should have the same comparators, otherwise the result is empty set.
// The new set consists of all elements that are in "set" but not in "another".
// Ref: https://proofwiki.org/wiki/Definition:Set_Difference
func (set *Set[E]) Difference(another *Set[E]) *Set[E] {
	result := NewWith(set.tree.Comparator)

	for it := set.Iterator(); it.Next(); {
		if !another.Contains(it.Value()) {
			result.Add(it.Value())
		}
	}

	return result
}

// UnmarshalJSON @implements json.Unmarshaler
func (set *Set[E]) UnmarshalJSON(bytes []byte) error {
	elements := []E{}
	err := json.Unmarshal(bytes, &elements)
	if err == nil {
		set.Clear()
		set.Add(elements...)
	}
	return err
}

// MarshalJSON @implements json.Marshaler
func (set *Set[E]) MarshalJSON() ([]byte, error) {
	return json.Marshal(set.Values())
}