forked from neetcode-gh/leetcode
-
Notifications
You must be signed in to change notification settings - Fork 0
/
146-LRU-Cache.js
155 lines (139 loc) · 3.78 KB
/
146-LRU-Cache.js
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
//////////////////////////////////////////////////////////////////////////////
// JavaScript Map Class Implementation
// This solution produces a lot less code, but is exposed to poor performance
// due to Map's internal maintenance of the order of properties. Constantly
// deleting and resetting properties upon each retrieval is costly.
//////////////////////////////////////////////////////////////////////////////
/**
* @param {number} capacity
*/
function LRUCache(capacity) {
this.capacity = capacity;
this.cacheMap = new Map();
}
/**
* @param {number} key
* @return {number}
*/
LRUCache.prototype.get = function (key) {
if (!this.cacheMap.has(key)) {
return -1;
}
const value = this.cacheMap.get(key);
this.cacheMap.delete(key);
this.cacheMap.set(key, value);
return value;
};
/**
* @param {number} key
* @param {number} value
* @return {void}
*/
LRUCache.prototype.put = function (key, value) {
if (this.cacheMap.has(key)) {
this.cacheMap.delete(key);
} else if (this.cacheMap.size === this.capacity) {
const leastRecentlyUsedKey = this.cacheMap.keys().next().value;
this.cacheMap.delete(leastRecentlyUsedKey);
}
this.cacheMap.set(key, value);
};
//////////////////////////////////////////////////////////////////////////////
// JavaScript Object Class Implementation
// This solution requires more code and space due to the need to separately
// define a doubly linked list and a hash map, but has better performance due
// to strictly maintaining constant time lookups and additions.
//////////////////////////////////////////////////////////////////////////////
class LRUNode {
/**
* @param {number} key
* @param {number} val
* @param {LRUNode=} next = `null`
* @constructor
*/
constructor(key, val, next = null) {
this.key = key;
this.val = val;
this.prev = null;
this.next = next;
}
}
class LRUCache {
/**
* @param {number} capacity
* @constructor
*/
constructor(capacity) {
this.head = null;
this.tail = null;
this.map = Object.create(null);
this.length = 0;
this.capacity = capacity;
}
/**
* @param {number} key
* @return {number}
*/
get(key) {
if (!(key in this.map)) {
return -1;
}
this.makeMostRecent(key);
return this.map[key].val;
}
/**
* @param {number} key
* @param {number} val
* @return {void}
*/
put(key, val) {
if (key in this.map) {
this.map[key].val = val;
this.makeMostRecent(key);
return;
}
if (this.length === this.capacity) {
delete this.map[this.tail.key];
if (this.head === this.tail) {
this.head = null;
this.tail = null;
} else {
this.tail = this.tail.prev;
this.tail.next = null;
}
} else {
++this.length;
}
const node = new LRUNode(key, val, this.head);
if (this.head) {
this.head.prev = node;
} else {
this.tail = node;
}
this.head = node;
this.map[key] = node;
}
/**
* @param {number} key
* @return {void}
*/
makeMostRecent(key) {
const node = this.map[key];
if (node === this.head) {
return node.val;
}
if (node.prev) {
node.prev.next = node.next;
}
if (node.next) {
node.next.prev = node.prev;
}
if (node === this.tail) {
this.tail = node.prev;
}
node.prev = null;
node.next = this.head;
this.head.prev = node;
this.head = node;
}
}