146. LRU Cache.py

class Node:
    def __init__(self, k, v):
        self.key = k
        self.val = v
        self.prev = None
        self.next = None
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class LRUCache:
    #Tail is the most accessed node. Head is need to be deleted while capacity is full in putting process..
    def __init__(self, capacity):
        """
        :type capacity: int
        """
        self.capacity = capacity
        self.dic = dict()
        self.head = Node(0, 0)
        self.tail = Node(0, 0)
        self.head.next = self.tail
        self.tail.prev = self.head

    def get(self, key):
        """
        :type key: int
        :rtype: int
        """
        if key in self.dic:
            n = self.dic[key]
            self._remove(n)
            self._add(n)
            return n.val
        return -1

    def put(self, key, value):
        """
        :type key: int
        :type value: int
        :rtype: None
        """
        if key in self.dic:
            self._remove(self.dic[key])
        n = Node(key, value)
        self._add(n)
        self.dic[key] = n
        if len(self.dic) > self.capacity:
            n = self.head.next
            self._remove(n)
            del self.dic[n.key]

    def _remove(self, node):
        p = node.prev
        n = node.next
        p.next = n
        n.prev = p

    def _add(self, node):
        p = self.tail.prev
        p.next = node
        self.tail.prev = node
        node.prev = p
        node.next = self.tail

obj = LRUCache(2)
obj.put(1,1)
obj.put(2,2)
obj.put(3,3)
print obj.get(2)


# Your LRUCache object will be instantiated and called as such:
# obj = LRUCache(capacity)
# param_1 = obj.get(key)
# obj.put(key,value)


from collections import OrderedDict
class LRUCache:
    def __init__(self, Capacity):
        self.size = Capacity
        self.cache = OrderedDict()

    def get(self, key):
        if key not in self.cache: return -1
        val = self.cache[key]
        self.cache.move_to_end(key)
        return val

    def put(self, key, val):
        if key in self.cache: del self.cache[key]
        self.cache[key] = val
        if len(self.cache) > self.size:
            self.cache.popitem(last=False)