Merge pull request #719 from fartem/146_LRU_Cache

2024-08-23 v. 6.5.4: added "146. LRU Cache"

Author: fartem

README.md

@@ -519,3 +519,4 @@ Profile on LeetCode: [fartem](https://leetcode.com/fartem/).
 | 138. Copy List with Random Pointer                              | [Link](https://leetcode.com/problems/copy-list-with-random-pointer/)                              | [Link](./lib/medium/138_copy_list_with_random_pointer.rb)                              | [Link](./test/medium/test_138_copy_list_with_random_pointer.rb)                              |
 | 142. Linked List Cycle II                                       | [Link](https://leetcode.com/problems/linked-list-cycle-ii/)                                       | [Link](./lib/medium/142_linked_list_cycle_ii.rb)                                       | [Link](./test/medium/test_142_linked_list_cycle_ii.rb)                                       |
 | 143. Reorder List                                               | [Link](https://leetcode.com/problems/reorder-list/)                                               | [Link](./lib/medium/143_reorder_list.rb)                                               | [Link](./test/medium/test_143_reorder_list.rb)                                               |
+| 146. LRU Cache                                                  | [Link](https://leetcode.com/problems/lru-cache/)                                                  | [Link](./lib/medium/146_lru_cache.rb)                                                  | [Link](./test/medium/test_146_lru_cache.rb)                                                  |

leetcode-ruby.gemspec

@@ -5,7 +5,7 @@ require 'English'
 ::Gem::Specification.new do |s|
   s.required_ruby_version = '>= 3.0'
   s.name = 'leetcode-ruby'
-  s.version = '6.5.3'
+  s.version = '6.5.4'
   s.license = 'MIT'
   s.files = ::Dir['lib/**/*.rb'] + %w[README.md]
   s.executable = 'leetcode-ruby'

lib/medium/146_lru_cache.rb

@@ -0,0 +1,88 @@
+# frozen_string_literal: true
+
+# https://leetcode.com/problems/lru-cache/
+class LRUCache
+  # @param {Integer} capacity
+  def initialize(capacity)
+    @capacity = capacity
+    @head = ::Node.new
+    @tail = ::Node.new
+    @cache = {}
+
+    @head.next = @tail
+    @tail.prev = @head
+  end
+
+  # @param {Integer} key
+  # @return {Integer}
+  def get(key)
+    node = @cache[key]
+
+    return -1 unless node
+
+    remove(node)
+    add(node)
+
+    node.val
+  end
+
+  # @param {Integer} key
+  # @param {Integer} value
+  # @return {Void}
+  def put(key, value)
+    node = @cache[key]
+
+    if node
+      remove(node)
+      node.val = value
+    else
+      if @cache.size == @capacity
+        @cache.delete(@tail.prev.key)
+        remove(@tail.prev)
+      end
+
+      node = ::Node.new
+      node.key = key
+      node.val = value
+      @cache[key] = node
+    end
+
+    add(node)
+  end
+
+  private
+
+  # @param {Node} node
+  # @return {Void}
+  def add(node)
+    nxt = @head.next
+    @head.next = node
+    nxt.prev = node
+    node.next = nxt
+    node.prev = @head
+  end
+
+  # @param {Node} node
+  # @return {Void}
+  def remove(node)
+    nxt = node.next
+    prev = node.prev
+    nxt.prev = prev
+    prev.next = nxt
+  end
+end
+
+private
+
+# Cache node
+class Node
+  attr_accessor :key, :val, :prev, :next
+
+  # Constructor with default parameters
+  def initialize
+    @key = 0
+    @val = 0
+    @prev = nil
+    @next = nil
+  end
+end

test/medium/test_146_lru_cache.rb

@@ -0,0 +1,36 @@
+# frozen_string_literal: true
+
+require_relative '../test_helper'
+require_relative '../../lib/medium/146_lru_cache'
+require 'minitest/autorun'
+
+class LRUCacheTest < ::Minitest::Test
+  def test_default_one
+    lru_cache = ::LRUCache.new(2)
+    lru_cache.put(1, 1)
+    lru_cache.put(2, 2)
+
+    assert_equal(1, lru_cache.get(1))
+
+    lru_cache.put(3, 3)
+
+    assert_equal(-1, lru_cache.get(2))
+
+    lru_cache.put(4, 4)
+
+    assert_equal(-1, lru_cache.get(1))
+    assert_equal(3, lru_cache.get(3))
+    assert_equal(4, lru_cache.get(4))
+  end
+
+  def test_additional_one
+    lru_cache = ::LRUCache.new(1)
+    lru_cache.put(1, 1)
+
+    assert_equal(1, lru_cache.get(1))
+
+    lru_cache.put(1, 2)
+
+    assert_equal(2, lru_cache.get(1))
+  end
+end