实现LFU缓存置换算法（Python）

关于LFU

最不经常使用算法，淘汰缓存时，把使用频率最小的淘汰掉，当多个节点使用频率相同时，按照FIFO算法淘汰。

具体实现（Python）

（代码中引进的双向链表内容请查看-->https://blog.csdn.net/huanglei305/article/details/99422314）

# -*- encoding=utf-8 -*-


from computer_principle.DoubleLinkedList import DoubleLinkedList, Node


class LFUNode(Node):
    def __init__(self, key, value):
        self.freq = 0
        super(LFUNode, self).__init__(key, value)


class LFUCache(object):

    def __init__(self, capacity):
        self.capacity = capacity
        self.map = {}
        # key: 频率, value: 频率对应的双向链表
        self.freq_map = {}
        self.size = 0

    # 更新节点频率的操作
    def __update_freq(self, node):
        freq = node.freq

        # 删除
        node = self.freq_map[freq].remove(node)
        if self.freq_map[freq].size == 0:
            del self.freq_map[freq]

        # 更新
        freq += 1
        node.freq = freq
        if freq not in self.freq_map:
            self.freq_map[freq] = DoubleLinkedList()
        self.freq_map[freq].append(node)

    def get(self, key):
        if key not in self.map:
            return -1
        node = self.map.get(key)
        self.__update_freq(node)
        return node.value

    def put(self, key, value):
        if self.capacity == 0:
            return

        # 缓存命中
        if key in self.map:
            node = self.map.get(key)
            node.value = value
            self.__update_freq(node)

        # 缓存没有命中
        else:
            if self.capacity == self.si***_freq = min(self.freq_map)
                node = self.freq_map[min_freq].pop()
                del self.map[node.key]
                self.size -= 1
            node = LFUNode(key, value)
            node.freq = 1
            self.map[key] = node
            if node.freq not in self.freq_map:
                self.freq_map[node.freq] = DoubleLinkedList()
            node = self.freq_map[node.freq].append(node)
            self.size += 1

    def print(self):
        print('***************************')
        for k, v in self.freq_map.items():
            print('Freq = %d' % k)
            self.freq_map[k].print()
        print('***************************')
        print()


if __name__ == '__main__':
    cache = LFUCache(2)
    cache.put(1, 1)
    cache.print()
    cache.put(2, 2)
    cache.print()
    print(cache.get(1))
    cache.print()
    cache.put(3, 3)
    cache.print()
    print(cache.get(2))
    cache.print()
    print(cache.get(3))
    cache.print()
    cache.put(4, 4)
    cache.print()
    print(cache.get(1))
    cache.print()
    print(cache.get(3))
    cache.print()
    print(cache.get(4))
    cache.print()

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实现双向链表（Python）https://blog.csdn.net/huanglei305/article/details/99422314

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