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Merge pull request #23 from emirpasic/bidi_map
- bidimap implemention as dual hashmap bidirectional map
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,25 @@ | ||
| // Copyright (c) 2015, Emir Pasic. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
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| package examples | ||
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| import "github.com/emirpasic/gods/maps/hashbidimap" | ||
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| // HashBidiMapExample to demonstrate basic usage of HashMap | ||
| func HashBidiMapExample() { | ||
| m := hashbidimap.New() // empty | ||
| m.Put(1, "x") // 1->x | ||
| m.Put(3, "b") // 1->x, 3->b (random order) | ||
| m.Put(1, "a") // 1->a, 3->b (random order) | ||
| m.Put(2, "b") // 1->a, 2->b (random order) | ||
| _, _ = m.GetKey("a") // 1, true | ||
| _, _ = m.Get(2) // b, true | ||
| _, _ = m.Get(3) // nil, false | ||
| _ = m.Values() // []interface {}{"a", "b"} (random order) | ||
| _ = m.Keys() // []interface {}{1, 2} (random order) | ||
| m.Remove(1) // 2->b | ||
| m.Clear() // empty | ||
| m.Empty() // true | ||
| m.Size() // 0 | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,102 @@ | ||
| // Copyright (c) 2015, Emir Pasic. All rights reserved. | ||
| // Use of this source code is governed by a BSD-style | ||
| // license that can be found in the LICENSE file. | ||
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| // Package hashbidimap implements a bidirectional map backed by two hashmaps. | ||
| // | ||
| // A bidirectional map, or hash bag, is an associative data structure in which the (key,value) pairs form a one-to-one correspondence. | ||
| // Thus the binary relation is functional in each direction: value can also act as a key to key. | ||
| // A pair (a,b) thus provides a unique coupling between 'a' and 'b' so that 'b' can be found when 'a' is used as a key and 'a' can be found when 'b' is used as a key. | ||
| // | ||
| // Elements are unordered in the map. | ||
| // | ||
| // Structure is not thread safe. | ||
| // | ||
| // Reference: https://en.wikipedia.org/wiki/Bidirectional_map | ||
| package hashbidimap | ||
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| import ( | ||
| "fmt" | ||
| "github.com/emirpasic/gods/maps" | ||
| "github.com/emirpasic/gods/maps/hashmap" | ||
| ) | ||
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| func assertMapImplementation() { | ||
| var _ maps.BidiMap = (*Map)(nil) | ||
| } | ||
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| // Map holds the elements in two hashmaps. | ||
| type Map struct { | ||
| forwardMap hashmap.Map | ||
| inverseMap hashmap.Map | ||
| } | ||
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| // New instantiates a bidirectional map. | ||
| func New() *Map { | ||
| return &Map{*hashmap.New(), *hashmap.New()} | ||
| } | ||
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| // Put inserts element into the map. | ||
| func (m *Map) Put(key interface{}, value interface{}) { | ||
| if valueByKey, ok := m.forwardMap.Get(key); ok { | ||
| m.inverseMap.Remove(valueByKey) | ||
| } | ||
| if keyByValue, ok := m.inverseMap.Get(value); ok { | ||
| m.forwardMap.Remove(keyByValue) | ||
| } | ||
| m.forwardMap.Put(key, value) | ||
| m.inverseMap.Put(value, key) | ||
| } | ||
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| // Get searches the element in the map by key and returns its value or nil if key is not found in map. | ||
| // Second return parameter is true if key was found, otherwise false. | ||
| func (m *Map) Get(key interface{}) (value interface{}, found bool) { | ||
| return m.forwardMap.Get(key) | ||
| } | ||
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| // GetKey searches the element in the map by value and returns its key or nil if value is not found in map. | ||
| // Second return parameter is true if value was found, otherwise false. | ||
| func (m *Map) GetKey(value interface{}) (key interface{}, found bool) { | ||
| return m.inverseMap.Get(value) | ||
| } | ||
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| // Remove removes the element from the map by key. | ||
| func (m *Map) Remove(key interface{}) { | ||
| if value, found := m.forwardMap.Get(key); found { | ||
| m.forwardMap.Remove(key) | ||
| m.inverseMap.Remove(value) | ||
| } | ||
| } | ||
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| // Empty returns true if map does not contain any elements | ||
| func (m *Map) Empty() bool { | ||
| return m.Size() == 0 | ||
| } | ||
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| // Size returns number of elements in the map. | ||
| func (m *Map) Size() int { | ||
| return m.forwardMap.Size() | ||
| } | ||
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| // Keys returns all keys (random order). | ||
| func (m *Map) Keys() []interface{} { | ||
| return m.forwardMap.Keys() | ||
| } | ||
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| // Values returns all values (random order). | ||
| func (m *Map) Values() []interface{} { | ||
| return m.inverseMap.Keys() | ||
| } | ||
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| // Clear removes all elements from the map. | ||
| func (m *Map) Clear() { | ||
| m.forwardMap.Clear() | ||
| m.inverseMap.Clear() | ||
| } | ||
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| // String returns a string representation of container | ||
| func (m *Map) String() string { | ||
| str := "HashMap\n" | ||
| str += fmt.Sprintf("%v", m.forwardMap) | ||
| return str | ||
| } |
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