From 1a16bc24fe94cc32b1bb43cb92dd60efd07f8954 Mon Sep 17 00:00:00 2001
From: lixingliang <lixingliang@iyunxiao.com>
Date: Fri, 1 Mar 2019 15:22:28 +0800
Subject: [PATCH] add 20_lru.go file

---
 go/20_lru/lru_cache.go      | 148 ++++++++++++++++++++++++++++++++++++
 go/20_lru/lru_cache_test.go |  67 ++++++++++++++++
 2 files changed, 215 insertions(+)
 create mode 100644 go/20_lru/lru_cache.go
 create mode 100644 go/20_lru/lru_cache_test.go

diff --git a/go/20_lru/lru_cache.go b/go/20_lru/lru_cache.go
new file mode 100644
index 0000000..4cd826e
--- /dev/null
+++ b/go/20_lru/lru_cache.go
@@ -0,0 +1,148 @@
+package lru_cache
+
+const (
+	hostbit = uint64(^uint(0)) == ^uint64(0)
+	LENGTH  = 100
+)
+
+type lruNode struct {
+	prev *lruNode
+	next *lruNode
+
+	key   int // lru key
+	value int // lru value
+
+	hnext *lruNode // 拉链
+}
+
+type LRUCache struct {
+	node []lruNode // hash list
+
+	head *lruNode // lru head node
+	tail *lruNode // lru tail node
+
+	capacity int //
+	used     int //
+}
+
+func Constructor(capacity int) LRUCache {
+	return LRUCache{
+		node:     make([]lruNode, LENGTH),
+		head:     nil,
+		tail:     nil,
+		capacity: capacity,
+		used:     0,
+	}
+}
+
+func (this *LRUCache) Get(key int) int {
+	if this.tail == nil {
+		return -1
+	}
+
+	if tmp := this.searchNode(key); tmp != nil {
+		this.moveToTail(tmp)
+		return tmp.value
+	}
+	return -1
+}
+
+func (this *LRUCache) Put(key int, value int) {
+	// 1. 首次插入数据
+	// 2. 插入数据不在 LRU 中
+	// 3. 插入数据在 LRU 中
+	// 4. 插入数据不在 LRU 中, 并且 LRU 已满
+
+	if tmp := this.searchNode(key); tmp != nil {
+		tmp.value = value
+		this.moveToTail(tmp)
+		return
+	}
+	this.addNode(key, value)
+
+	if this.used > this.capacity {
+		this.delNode()
+	}
+}
+
+func (this *LRUCache) addNode(key int, value int) {
+	newNode := &lruNode{
+		key:   key,
+		value: value,
+	}
+
+	tmp := &this.node[hash(key)]
+	newNode.hnext = tmp.hnext
+	tmp.hnext = newNode
+	this.used++
+
+	if this.tail == nil {
+		this.tail, this.head = newNode, newNode
+		return
+	}
+	this.tail.next = newNode
+	newNode.prev = this.tail
+	this.tail = newNode
+}
+
+func (this *LRUCache) delNode() {
+	if this.head == nil {
+		return
+	}
+	prev := &this.node[hash(this.head.key)]
+	tmp := prev.hnext
+
+	for tmp != nil && tmp.key != this.head.key {
+		prev = tmp
+		tmp = tmp.hnext
+	}
+	if tmp == nil {
+		return
+	}
+	prev.hnext = tmp.hnext
+	this.head = this.head.next
+	this.head.prev = nil
+	this.used--
+}
+
+func (this *LRUCache) searchNode(key int) *lruNode {
+	if this.tail == nil {
+		return nil
+	}
+
+	// 查找
+	tmp := this.node[hash(key)].hnext
+	for tmp != nil {
+		if tmp.key == key {
+			return tmp
+		}
+		tmp = tmp.hnext
+	}
+	return nil
+}
+
+func (this *LRUCache) moveToTail(node *lruNode) {
+	if this.tail == node {
+		return
+	}
+	if this.head == node {
+		this.head = node.next
+		this.head.prev = nil
+	} else {
+		node.next.prev = node.prev
+		node.prev.next = node.next
+	}
+
+	node.next = nil
+	this.tail.next = node
+	node.prev = this.tail
+
+	this.tail = node
+}
+
+func hash(key int) int {
+	if hostbit {
+		return (key ^ (key >> 32)) & (LENGTH - 1)
+	}
+	return (key ^ (key >> 16)) & (LENGTH - 1)
+}
diff --git a/go/20_lru/lru_cache_test.go b/go/20_lru/lru_cache_test.go
new file mode 100644
index 0000000..45fc93c
--- /dev/null
+++ b/go/20_lru/lru_cache_test.go
@@ -0,0 +1,67 @@
+package lru_cache
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func Test_Hostbit(t *testing.T) {
+	fmt.Println(hostbit)
+}
+
+func Test_LRU(t *testing.T) {
+	lru := Constructor(2)
+
+	lru.Put(1, 1)
+	lru.Put(2, 2)
+	assert.Equal(t, lru.Get(1), 1)  // returns 1
+	lru.Put(3, 3)                   // evicts key 2
+	assert.Equal(t, lru.Get(2), -1) // returns -1 (not found)
+	lru.Put(4, 4)                   // evicts key 1
+	assert.Equal(t, lru.Get(1), -1) // returns -1 (not found)
+	assert.Equal(t, lru.Get(3), 3)  // returns 3
+	assert.Equal(t, lru.Get(4), 4)  // returns 4
+}
+
+func Test_LRU_PutGet(t *testing.T) {
+	lru := Constructor(1)
+
+	lru.Put(1, 2)
+	assert.Equal(t, lru.Get(1), 2) // returns 2
+}
+
+func Test_LRU_PutGetPutGetGet(t *testing.T) {
+	lru := Constructor(1)
+
+	lru.Put(2, 1)
+	assert.Equal(t, lru.Get(2), 1) // returns 1
+	lru.Put(3, 2)
+	assert.Equal(t, lru.Get(2), -1) // returns -1
+	assert.Equal(t, lru.Get(3), 2)  // returns 2
+}
+
+func Test_LRU_PPGPPG(t *testing.T) {
+	lru := Constructor(2)
+
+	lru.Put(2, 1)
+	lru.Put(2, 2)
+	assert.Equal(t, lru.Get(2), 2) // returns 2
+	lru.Put(1, 4)
+	lru.Put(4, 1)
+	assert.Equal(t, lru.Get(2), -1) // returns -1
+	assert.Equal(t, lru.Get(3), -1) // returns -1
+}
+
+func Test_LRU_PPGPPG_2(t *testing.T) {
+	lru := Constructor(2)
+
+	lru.Put(2, 1)
+	lru.Put(2, 2)
+	assert.Equal(t, lru.Get(2), 2) // returns 2
+	lru.Put(1, 1)
+	lru.Put(4, 1)
+	assert.Equal(t, lru.Get(2), -1) // returns -1
+	assert.Equal(t, lru.Get(3), -1) // returns -1
+}