London | 26-SDC-Jul | AYK | Sprint 2 | Implement an LRU cache in Python

Sprint-2/implement_lru_cache/lru_cache.py

@@ -0,0 +1,65 @@
+class Node:
+    def __init__(self,key,value):
+        self.key = key
+        self.value = value
+        self.prev = None   # point to previous node
+        self.next = None  # point to next node
+
+
+class LruCache:
+    def __init__(self,limit):
+        self.limit = limit
+        self.cache = {}  # for store node objects
+
+        #dummy nodes for making insert and remove easier
+        self.head = Node(None,None)
+        self.tail = Node(None,None)
+
+        #linking two dummy nodes
+        self.head.next = self.tail
+        self.tail.prev =  self.head
+
+    def remove(self,node):
+        node.prev.next = node.next
+        node.next.prev = node.prev
+
+    def add_to_front(self,node):
+        node.next = self.head.next
+        node.prev = self.head
+
+        self.head.next.prev = node
+        self.head.next = node
+
+    def move_to_front (self,node):
+        self.remove(node)
+        self.add_to_front(node)
+
+    def get (self,key):
+        if key not in self.cache:
+            return None
+
+        node = self.cache[key]
+        self.move_to_front(node)
+        return node.value
+
+    def set(self,key,value):
+        if self.limit <= 0:
+            return
+        if key in self.cache:
+            node = self.cache[key]
+            node.value = value
+            self.move_to_front(node)
+            return
+        if len(self.cache) >= self.limit:
+            lru_node = self.tail.prev
+            self.remove(lru_node)
+            del self.cache[lru_node.key]
+
+            new_node = Node(key,value)
+            self.cache[key] = new_node
+            self.add_to_front(new_node)
+
+
+
+
+