From 39c576248c7479e42499613723dc4fdc9d82bad4 Mon Sep 17 00:00:00 2001
From: dudaodong <lanliddd.2007@163.com>
Date: Thu, 29 Dec 2022 11:43:14 +0800
Subject: [PATCH] test: add examples for lrucache

---
 algorithm/lrucache.go              | 121 +++++++++++++++++++++++++++++
 algorithm/lrucache_example_test.go |  79 +++++++++++++++++++
 algorithm/lrucache_test.go         |  33 ++++++++
 3 files changed, 233 insertions(+)
 create mode 100644 algorithm/lrucache.go
 create mode 100644 algorithm/lrucache_example_test.go
 create mode 100644 algorithm/lrucache_test.go

diff --git a/algorithm/lrucache.go b/algorithm/lrucache.go
new file mode 100644
index 0000000..c1c737d
--- /dev/null
+++ b/algorithm/lrucache.go
@@ -0,0 +1,121 @@
+package algorithm
+
+type lruNode[K comparable, V any] struct {
+	key   K
+	value V
+	pre   *lruNode[K, V]
+	next  *lruNode[K, V]
+}
+
+// newLruNode return a lruNode pointer
+func newLruNode[K comparable, V any](key K, value V) *lruNode[K, V] {
+	return &lruNode[K, V]{
+		key:   key,
+		value: value,
+		pre:   nil,
+		next:  nil,
+	}
+}
+
+// LRUCache lru cache (thread unsafe)
+type LRUCache[K comparable, V any] struct {
+	cache    map[K]*lruNode[K, V]
+	head     *lruNode[K, V]
+	tail     *lruNode[K, V]
+	capacity int
+	length   int
+}
+
+// NewLRUCache creates a LRUCache pointer instance.
+func NewLRUCache[K comparable, V any](capacity int) *LRUCache[K, V] {
+	return &LRUCache[K, V]{
+		cache:    make(map[K]*lruNode[K, V], capacity),
+		head:     nil,
+		tail:     nil,
+		capacity: capacity,
+		length:   0,
+	}
+}
+
+// Get value of key from lru cache.
+// Play: https://go.dev/play/p/iUynEfOP8G0
+func (l *LRUCache[K, V]) Get(key K) (V, bool) {
+	var value V
+
+	node, ok := l.cache[key]
+	if ok {
+		l.moveToHead(node)
+		return node.value, true
+	}
+
+	return value, false
+}
+
+// Put value of key into lru cache.
+// Play: https://go.dev/play/p/iUynEfOP8G0
+func (l *LRUCache[K, V]) Put(key K, value V) {
+	node, ok := l.cache[key]
+	if !ok {
+		newNode := newLruNode(key, value)
+		l.cache[key] = newNode
+		l.addNode(newNode)
+
+		if len(l.cache) > l.capacity {
+			oldKey := l.deleteNode(l.head)
+			delete(l.cache, oldKey)
+		}
+	} else {
+		node.value = value
+		l.moveToHead(node)
+	}
+	l.length = len(l.cache)
+}
+
+// Delete item from lru cache.
+func (l *LRUCache[K, V]) Delete(key K) bool {
+	node, ok := l.cache[key]
+	if ok {
+		key := l.deleteNode(node)
+		delete(l.cache, key)
+		return true
+	}
+
+	return false
+}
+
+// Len returns the number of items in the cache.
+func (l *LRUCache[K, V]) Len() int {
+	return l.length
+}
+
+func (l *LRUCache[K, V]) addNode(node *lruNode[K, V]) {
+	if l.tail != nil {
+		l.tail.next = node
+		node.pre = l.tail
+		node.next = nil
+	}
+	l.tail = node
+	if l.head == nil {
+		l.head = node
+	}
+}
+
+func (l *LRUCache[K, V]) deleteNode(node *lruNode[K, V]) K {
+	if node == l.tail {
+		l.tail = l.tail.pre
+	} else if node == l.head {
+		l.head = l.head.next
+	} else {
+		node.pre.next = node.next
+		node.next.pre = node.pre
+	}
+	return node.key
+}
+
+func (l *LRUCache[K, V]) moveToHead(node *lruNode[K, V]) {
+	if l.tail == node {
+		return
+	}
+	l.deleteNode(node)
+	l.addNode(node)
+}
diff --git a/algorithm/lrucache_example_test.go b/algorithm/lrucache_example_test.go
new file mode 100644
index 0000000..b792b74
--- /dev/null
+++ b/algorithm/lrucache_example_test.go
@@ -0,0 +1,79 @@
+package algorithm
+
+import "fmt"
+
+func ExampleLRUCache_Put() {
+	cache := NewLRUCache[int, int](2)
+
+	cache.Put(1, 1)
+	cache.Put(2, 2)
+
+	result1, ok1 := cache.Get(1)
+	result2, ok2 := cache.Get(2)
+	result3, ok3 := cache.Get(3)
+
+	fmt.Println(result1, ok1)
+	fmt.Println(result2, ok2)
+	fmt.Println(result3, ok3)
+
+	// Output:
+	// 1 true
+	// 2 true
+	// 0 false
+}
+
+func ExampleLRUCache_Get() {
+	cache := NewLRUCache[int, int](2)
+
+	cache.Put(1, 1)
+	cache.Put(2, 2)
+
+	result1, ok1 := cache.Get(1)
+	result2, ok2 := cache.Get(2)
+	result3, ok3 := cache.Get(3)
+
+	fmt.Println(result1, ok1)
+	fmt.Println(result2, ok2)
+	fmt.Println(result3, ok3)
+
+	// Output:
+	// 1 true
+	// 2 true
+	// 0 false
+}
+
+func ExampleLRUCache_Delete() {
+	cache := NewLRUCache[int, int](2)
+
+	cache.Put(1, 1)
+	cache.Put(2, 2)
+
+	result1, ok1 := cache.Get(1)
+
+	ok2 := cache.Delete(2)
+
+	_, ok3 := cache.Get(2)
+
+	fmt.Println(result1, ok1)
+	fmt.Println(ok2)
+	fmt.Println(ok3)
+
+	// Output:
+	// 1 true
+	// true
+	// false
+}
+
+func ExampleLRUCache_Len() {
+	cache := NewLRUCache[int, int](2)
+
+	cache.Put(1, 1)
+	cache.Put(2, 2)
+
+	result := cache.Len()
+
+	fmt.Println(result)
+
+	// Output:
+	// 2
+}
diff --git a/algorithm/lrucache_test.go b/algorithm/lrucache_test.go
new file mode 100644
index 0000000..7d62b68
--- /dev/null
+++ b/algorithm/lrucache_test.go
@@ -0,0 +1,33 @@
+package algorithm
+
+import (
+	"testing"
+
+	"github.com/duke-git/lancet/v2/internal"
+)
+
+func TestLRUCache(t *testing.T) {
+	asssert := internal.NewAssert(t, "TestLRUCache")
+
+	cache := NewLRUCache[int, int](3)
+
+	cache.Put(1, 1)
+	cache.Put(2, 2)
+	cache.Put(3, 3)
+
+	asssert.Equal(3, cache.Len())
+
+	v, ok := cache.Get(1)
+	asssert.Equal(true, ok)
+	asssert.Equal(1, v)
+
+	v, ok = cache.Get(2)
+	asssert.Equal(true, ok)
+	asssert.Equal(2, v)
+
+	ok = cache.Delete(2)
+	asssert.Equal(true, ok)
+
+	_, ok = cache.Get(2)
+	asssert.Equal(false, ok)
+}