问题描述
go没有提供set数据结构，请用map实现set
要点
需要支持方法：
- Add 添加元素
- Remove 删除元素
- Cardinality 获取 Set 长度
- Clear 清空 Set
- Contains 检测元素是否在 Set 中
- Pop() 随机删除一个元素并返回被删除的元素
- ToSlice() []interface{} 转换成slice返回
拓展
- Clone 复制 Set
- Difference(other Set) Set 返回和另一个Set的差集
- Equal(other Set) bool 判断和另一个Set是否相等
- Intersect(other Set) Set 返回和另一个Set的交集
- SymmetricDifference(other Set) Set 返回不在交集中的元素的集合
- Union(other Set) Set 返回并集
- 实现一个线程安全的版本
实现
//set.go
// Package mapset implements a simple and generic set collection.
// Items stored within it are unordered and unique. It supports
// typical set operations: membership testing, intersection, union,
// difference, symmetric difference and cloning.
//
// Package mapset provides two implementations of the Set
// interface. The default implementation is safe for concurrent
// access, but a non-thread-safe implementation is also provided for
// programs that can benefit from the slight speed improvement and
// that can enforce mutual exclusion through other means.
package mapset
// Set is the primary interface provided by the mapset package. It
// represents an unordered set of data and a large number of
// operations that can be applied to that set.
type Set interface {
// Adds an element to the set. Returns whether
// the item was added.
Add(i interface{}) bool
// Returns the number of elements in the set.
Cardinality() int
// Removes all elements from the set, leaving
// the empty set.
Clear()
// Returns a clone of the set using the same
// implementation, duplicating all keys.
Clone() Set
// Returns whether the given items
// are all in the set.
Contains(i ...interface{}) bool
// Returns the difference between this set
// and other. The returned set will contain
// all elements of this set that are not also
// elements of other.
//
// Note that the argument to Difference
// must be of the same type as the receiver
// of the method. Otherwise, Difference will
// panic.
Difference(other Set) Set
// Determines if two sets are equal to each
// other. If they have the same cardinality
// and contain the same elements, they are
// considered equal. The order in which
// the elements were added is irrelevant.
//
// Note that the argument to Equal must be
// of the same type as the receiver of the
// method. Otherwise, Equal will panic.
Equal(other Set) bool
// Returns a new set containing only the elements
// that exist only in both sets.
//
// Note that the argument to Intersect
// must be of the same type as the receiver
// of the method. Otherwise, Intersect will
// panic.
Intersect(other Set) Set
// Determines if every element in this set is in
// the other set but the two sets are not equal.
//
// Note that the argument to IsProperSubset
// must be of the same type as the receiver
// of the method. Otherwise, IsProperSubset
// will panic.
IsProperSubset(other Set) bool
// Determines if every element in the other set
// is in this set but the two sets are not
// equal.
//
// Note that the argument to IsSuperset
// must be of the same type as the receiver
// of the method. Otherwise, IsSuperset will
// panic.
IsProperSuperset(other Set) bool
// Determines if every element in this set is in
// the other set.
//
// Note that the argument to IsSubset
// must be of the same type as the receiver
// of the method. Otherwise, IsSubset will
// panic.
IsSubset(other Set) bool
// Determines if every element in the other set
// is in this set.
//
// Note that the argument to IsSuperset
// must be of the same type as the receiver
// of the method. Otherwise, IsSuperset will
// panic.
IsSuperset(other Set) bool
// Iterates over elements and executes the passed func against each element.
// If passed func returns true, stop iteration at the time.
Each(func(interface{}) bool)
// Returns a channel of elements that you can
// range over.
Iter() <-chan interface{}
// Returns an Iterator object that you can
// use to range over the set.
Iterator() *Iterator
// Remove a single element from the set.
Remove(i interface{})
// Provides a convenient string representation
// of the current state of the set.
String() string
// Returns a new set with all elements which are
// in either this set or the other set but not in both.
//
// Note that the argument to SymmetricDifference
// must be of the same type as the receiver
// of the method. Otherwise, SymmetricDifference
// will panic.
SymmetricDifference(other Set) Set
// Returns a new set with all elements in both sets.
//
// Note that the argument to Union must be of the
// same type as the receiver of the method.
// Otherwise, IsSuperset will panic.
Union(other Set) Set
// Pop removes and returns an arbitrary item from the set.
Pop() interface{}
// Returns all subsets of a given set (Power Set).
PowerSet() Set
// Returns the Cartesian Product of two sets.
CartesianProduct(other Set) Set
// Returns the members of the set as a slice.
ToSlice() []interface{}
}
// NewSet creates and returns a reference to an empty set. Operations
// on the resulting set are thread-safe.
func NewSet(s ...interface{}) Set {
set := newThreadSafeSet()
for _, item := range s {
set.Add(item)
}
return &set
}
// NewSetWith creates and returns a new set with the given elements.
// Operations on the resulting set are thread-safe.
func NewSetWith(elts ...interface{}) Set {
return NewSetFromSlice(elts)
}
// NewSetFromSlice creates and returns a reference to a set from an
// existing slice. Operations on the resulting set are thread-safe.
func NewSetFromSlice(s []interface{}) Set {
a := NewSet(s...)
return a
}
// NewThreadUnsafeSet creates and returns a reference to an empty set.
// Operations on the resulting set are not thread-safe.
func NewThreadUnsafeSet() Set {
set := newThreadUnsafeSet()
return &set
}
// NewThreadUnsafeSetFromSlice creates and returns a reference to a
// set from an existing slice. Operations on the resulting set are
// not thread-safe.
func NewThreadUnsafeSetFromSlice(s []interface{}) Set {
a := NewThreadUnsafeSet()
for _, item := range s {
a.Add(item)
}
return a
}
// iterator.go
package mapset
// Iterator defines an iterator over a Set, its C channel can be used to range over the Set's
// elements.
type Iterator struct {
C <-chan interface{}
stop chan struct{}
}
// Stop stops the Iterator, no further elements will be received on C, C will be closed.
func (i *Iterator) Stop() {
// Allows for Stop() to be called multiple times
// (close() panics when called on already closed channel)
defer func() {
recover()
}()
close(i.stop)
// Exhaust any remaining elements.
for range i.C {
}
}
// newIterator returns a new Iterator instance together with its item and stop channels.
func newIterator() (*Iterator, chan<- interface{}, <-chan struct{}) {
itemChan := make(chan interface{})
stopChan := make(chan struct{})
return &Iterator{
C: itemChan,
stop: stopChan,
}, itemChan, stopChan
}
// threadunsafe.go
package mapset
import (
"bytes"
"encoding/json"
"fmt"
"reflect"
"strings"
)
type threadUnsafeSet map[interface{}]struct{}
// An OrderedPair represents a 2-tuple of values.
type OrderedPair struct {
First interface{}
Second interface{}
}
func newThreadUnsafeSet() threadUnsafeSet {
return make(threadUnsafeSet)
}
// Equal says whether two 2-tuples contain the same values in the same order.
func (pair *OrderedPair) Equal(other OrderedPair) bool {
if pair.First == other.First &&
pair.Second == other.Second {
return true
}
return false
}
func (set *threadUnsafeSet) Add(i interface{}) bool {
_, found := (*set)[i]
if found {
return false //False if it existed already
}
(*set)[i] = struct{}{}
return true
}
func (set *threadUnsafeSet) Contains(i ...interface{}) bool {
for _, val := range i {
if _, ok := (*set)[val]; !ok {
return false
}
}
return true
}
func (set *threadUnsafeSet) IsSubset(other Set) bool {
_ = other.(*threadUnsafeSet)
if set.Cardinality() > other.Cardinality() {
return false
}
for elem := range *set {
if !other.Contains(elem) {
return false
}
}
return true
}
func (set *threadUnsafeSet) IsProperSubset(other Set) bool {
return set.IsSubset(other) && !set.Equal(other)
}
func (set *threadUnsafeSet) IsSuperset(other Set) bool {
return other.IsSubset(set)
}
func (set *threadUnsafeSet) IsProperSuperset(other Set) bool {
return set.IsSuperset(other) && !set.Equal(other)
}
func (set *threadUnsafeSet) Union(other Set) Set {
o := other.(*threadUnsafeSet)
unionedSet := newThreadUnsafeSet()
for elem := range *set {
unionedSet.Add(elem)
}
for elem := range *o {
unionedSet.Add(elem)
}
return &unionedSet
}
func (set *threadUnsafeSet) Intersect(other Set) Set {
o := other.(*threadUnsafeSet)
intersection := newThreadUnsafeSet()
// loop over smaller set
if set.Cardinality() < other.Cardinality() {
for elem := range *set {
if other.Contains(elem) {
intersection.Add(elem)
}
}
} else {
for elem := range *o {
if set.Contains(elem) {
intersection.Add(elem)
}
}
}
return &intersection
}
func (set *threadUnsafeSet) Difference(other Set) Set {
_ = other.(*threadUnsafeSet)
difference := newThreadUnsafeSet()
for elem := range *set {
if !other.Contains(elem) {
difference.Add(elem)
}
}
return &difference
}
func (set *threadUnsafeSet) SymmetricDifference(other Set) Set {
_ = other.(*threadUnsafeSet)
aDiff := set.Difference(other)
bDiff := other.Difference(set)
return aDiff.Union(bDiff)
}
func (set *threadUnsafeSet) Clear() {
*set = newThreadUnsafeSet()
}
func (set *threadUnsafeSet) Remove(i interface{}) {
delete(*set, i)
}
func (set *threadUnsafeSet) Cardinality() int {
return len(*set)
}
func (set *threadUnsafeSet) Each(cb func(interface{}) bool) {
for elem := range *set {
if cb(elem) {
break
}
}
}
func (set *threadUnsafeSet) Iter() <-chan interface{} {
ch := make(chan interface{})
go func() {
for elem := range *set {
ch <- elem
}
close(ch)
}()
return ch
}
func (set *threadUnsafeSet) Iterator() *Iterator {
iterator, ch, stopCh := newIterator()
go func() {
L:
for elem := range *set {
select {
case <-stopCh:
break L
case ch <- elem:
}
}
close(ch)
}()
return iterator
}
func (set *threadUnsafeSet) Equal(other Set) bool {
_ = other.(*threadUnsafeSet)
if set.Cardinality() != other.Cardinality() {
return false
}
for elem := range *set {
if !other.Contains(elem) {
return false
}
}
return true
}
func (set *threadUnsafeSet) Clone() Set {
clonedSet := newThreadUnsafeSet()
for elem := range *set {
clonedSet.Add(elem)
}
return &clonedSet
}
func (set *threadUnsafeSet) String() string {
items := make([]string, 0, len(*set))
for elem := range *set {
items = append(items, fmt.Sprintf("%v", elem))
}
return fmt.Sprintf("Set{%s}", strings.Join(items, ", "))
}
// String outputs a 2-tuple in the form "(A, B)".
func (pair OrderedPair) String() string {
return fmt.Sprintf("(%v, %v)", pair.First, pair.Second)
}
func (set *threadUnsafeSet) Pop() interface{} {
for item := range *set {
delete(*set, item)
return item
}
return nil
}
func (set *threadUnsafeSet) PowerSet() Set {
powSet := NewThreadUnsafeSet()
nullset := newThreadUnsafeSet()
powSet.Add(&nullset)
for es := range *set {
u := newThreadUnsafeSet()
j := powSet.Iter()
for er := range j {
p := newThreadUnsafeSet()
if reflect.TypeOf(er).Name() == "" {
k := er.(*threadUnsafeSet)
for ek := range *(k) {
p.Add(ek)
}
} else {
p.Add(er)
}
p.Add(es)
u.Add(&p)
}
powSet = powSet.Union(&u)
}
return powSet
}
func (set *threadUnsafeSet) CartesianProduct(other Set) Set {
o := other.(*threadUnsafeSet)
cartProduct := NewThreadUnsafeSet()
for i := range *set {
for j := range *o {
elem := OrderedPair{First: i, Second: j}
cartProduct.Add(elem)
}
}
return cartProduct
}
func (set *threadUnsafeSet) ToSlice() []interface{} {
keys := make([]interface{}, 0, set.Cardinality())
for elem := range *set {
keys = append(keys, elem)
}
return keys
}
// MarshalJSON creates a JSON array from the set, it marshals all elements
func (set *threadUnsafeSet) MarshalJSON() ([]byte, error) {
items := make([]string, 0, set.Cardinality())
for elem := range *set {
b, err := json.Marshal(elem)
if err != nil {
return nil, err
}
items = append(items, string(b))
}
return []byte(fmt.Sprintf("[%s]", strings.Join(items, ","))), nil
}
// UnmarshalJSON recreates a set from a JSON array, it only decodes
// primitive types. Numbers are decoded as json.Number.
func (set *threadUnsafeSet) UnmarshalJSON(b []byte) error {
var i []interface{}
d := json.NewDecoder(bytes.NewReader(b))
d.UseNumber()
err := d.Decode(&i)
if err != nil {
return err
}
for _, v := range i {
switch t := v.(type) {
case []interface{}, map[string]interface{}:
continue
default:
set.Add(t)
}
}
return nil
}
// threadsafe.go
package mapset
import "sync"
type threadSafeSet struct {
s threadUnsafeSet
sync.RWMutex
}
func newThreadSafeSet() threadSafeSet {
return threadSafeSet{s: newThreadUnsafeSet()}
}
func (set *threadSafeSet) Add(i interface{}) bool {
set.Lock()
ret := set.s.Add(i)
set.Unlock()
return ret
}
func (set *threadSafeSet) Contains(i ...interface{}) bool {
set.RLock()
ret := set.s.Contains(i...)
set.RUnlock()
return ret
}
func (set *threadSafeSet) IsSubset(other Set) bool {
o := other.(*threadSafeSet)
set.RLock()
o.RLock()
ret := set.s.IsSubset(&o.s)
set.RUnlock()
o.RUnlock()
return ret
}
func (set *threadSafeSet) IsProperSubset(other Set) bool {
o := other.(*threadSafeSet)
set.RLock()
defer set.RUnlock()
o.RLock()
defer o.RUnlock()
return set.s.IsProperSubset(&o.s)
}
func (set *threadSafeSet) IsSuperset(other Set) bool {
return other.IsSubset(set)
}
func (set *threadSafeSet) IsProperSuperset(other Set) bool {
return other.IsProperSubset(set)
}
func (set *threadSafeSet) Union(other Set) Set {
o := other.(*threadSafeSet)
set.RLock()
o.RLock()
unsafeUnion := set.s.Union(&o.s).(*threadUnsafeSet)
ret := &threadSafeSet{s: *unsafeUnion}
set.RUnlock()
o.RUnlock()
return ret
}
func (set *threadSafeSet) Intersect(other Set) Set {
o := other.(*threadSafeSet)
set.RLock()
o.RLock()
unsafeIntersection := set.s.Intersect(&o.s).(*threadUnsafeSet)
ret := &threadSafeSet{s: *unsafeIntersection}
set.RUnlock()
o.RUnlock()
return ret
}
func (set *threadSafeSet) Difference(other Set) Set {
o := other.(*threadSafeSet)
set.RLock()
o.RLock()
unsafeDifference := set.s.Difference(&o.s).(*threadUnsafeSet)
ret := &threadSafeSet{s: *unsafeDifference}
set.RUnlock()
o.RUnlock()
return ret
}
func (set *threadSafeSet) SymmetricDifference(other Set) Set {
o := other.(*threadSafeSet)
set.RLock()
o.RLock()
unsafeDifference := set.s.SymmetricDifference(&o.s).(*threadUnsafeSet)
ret := &threadSafeSet{s: *unsafeDifference}
set.RUnlock()
o.RUnlock()
return ret
}
func (set *threadSafeSet) Clear() {
set.Lock()
set.s = newThreadUnsafeSet()
set.Unlock()
}
func (set *threadSafeSet) Remove(i interface{}) {
set.Lock()
delete(set.s, i)
set.Unlock()
}
func (set *threadSafeSet) Cardinality() int {
set.RLock()
defer set.RUnlock()
return len(set.s)
}
func (set *threadSafeSet) Each(cb func(interface{}) bool) {
set.RLock()
for elem := range set.s {
if cb(elem) {
break
}
}
set.RUnlock()
}
func (set *threadSafeSet) Iter() <-chan interface{} {
ch := make(chan interface{})
go func() {
set.RLock()
for elem := range set.s {
ch <- elem
}
close(ch)
set.RUnlock()
}()
return ch
}
func (set *threadSafeSet) Iterator() *Iterator {
iterator, ch, stopCh := newIterator()
go func() {
set.RLock()
L:
for elem := range set.s {
select {
case <-stopCh:
break L
case ch <- elem:
}
}
close(ch)
set.RUnlock()
}()
return iterator
}
func (set *threadSafeSet) Equal(other Set) bool {
o := other.(*threadSafeSet)
set.RLock()
o.RLock()
ret := set.s.Equal(&o.s)
set.RUnlock()
o.RUnlock()
return ret
}
func (set *threadSafeSet) Clone() Set {
set.RLock()
unsafeClone := set.s.Clone().(*threadUnsafeSet)
ret := &threadSafeSet{s: *unsafeClone}
set.RUnlock()
return ret
}
func (set *threadSafeSet) String() string {
set.RLock()
ret := set.s.String()
set.RUnlock()
return ret
}
func (set *threadSafeSet) PowerSet() Set {
set.RLock()
unsafePowerSet := set.s.PowerSet().(*threadUnsafeSet)
set.RUnlock()
ret := &threadSafeSet{s: newThreadUnsafeSet()}
for subset := range unsafePowerSet.Iter() {
unsafeSubset := subset.(*threadUnsafeSet)
ret.Add(&threadSafeSet{s: *unsafeSubset})
}
return ret
}
func (set *threadSafeSet) Pop() interface{} {
set.Lock()
defer set.Unlock()
return set.s.Pop()
}
func (set *threadSafeSet) CartesianProduct(other Set) Set {
o := other.(*threadSafeSet)
set.RLock()
o.RLock()
unsafeCartProduct := set.s.CartesianProduct(&o.s).(*threadUnsafeSet)
ret := &threadSafeSet{s: *unsafeCartProduct}
set.RUnlock()
o.RUnlock()
return ret
}
func (set *threadSafeSet) ToSlice() []interface{} {
keys := make([]interface{}, 0, set.Cardinality())
set.RLock()
for elem := range set.s {
keys = append(keys, elem)
}
set.RUnlock()
return keys
}
func (set *threadSafeSet) MarshalJSON() ([]byte, error) {
set.RLock()
b, err := set.s.MarshalJSON()
set.RUnlock()
return b, err
}
func (set *threadSafeSet) UnmarshalJSON(p []byte) error {
set.RLock()
err := set.s.UnmarshalJSON(p)
set.RUnlock()
return err
}
源码来自：https://github.com/deckarep/golang-set
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