neetcode-gh · Ahmad-A0 · Nov 2, 2022 · Oct 23, 2022 · Nov 2, 2022
diff --git a/ruby/146-LRU-Cache.rb b/ruby/146-LRU-Cache.rb
@@ -0,0 +1,74 @@
+class LRUCache
+
+=begin
+    :type capacity: Integer
+=end
+    def initialize(capacity)
+        @capacity = capacity
+        @cache = {}
+        @l = Node.new()
+        @r = Node.new()
+        @l.next = @r
+        @r.prev = @l
+    end
+
+
+=begin
+    :type key: Integer
+    :rtype: Integer
+=end
+    def get(key)
+        return -1 unless @cache.key?(key)
+
+        remove(@cache[key])
+        insert(@cache[key])
+        @cache[key].value
+    end
+
+
+=begin
+    :type key: Integer
+    :type value: Integer
+    :rtype: Void
+=end
+    def put(key, value)
+        remove(@cache[key]) if @cache.key?(key)
+
+        @cache[key] = Node.new(key, value)
+        insert(@cache[key])
+        evict if @capacity < @cache.size
+    end
+
+    private
+    def remove(node)
+        prev = node.prev
+        nxt = node.next
+
+        prev.next = nxt
+        nxt.prev = prev
+    end
+
+    def insert(node)
+        prev = @r.prev
+        prev.next = node
+        @r.prev = node
+
+        node.prev = prev
+        node.next = @r
+    end
+
+    def evict
+        lru = @l.next
+        remove(lru)
+        @cache.delete(lru.key)
+    end
+
+    class Node
+        attr_accessor :value, :prev, :next, :key
+
+        def initialize(key = 0, val = nil)
+            self.value = val
+            self.key = key
+        end
+    end
+end