C++实现支持泛型的LFU详解

template<typename K, typename V>
struct ListNode {
    K key;
    V value;
    int freq;
    long cur;
    bool operator<(const ListNode &x) const {
        if (freq < x.freq)
            return true;
        else if (freq == x.freq)
            return cur < x.cur;
        else
            return false;
    }
};

#include <map>
#include <set>
#include <unordered_map>
using namespace std;
template<typename K, typename V>
struct ListNode {
    K key;
    V value;
    int freq;
    long cur;
    bool operator<(const ListNode &x) const {
        if (freq < x.freq)
            return true;
        else if (freq == x.freq)
            return cur < x.cur;
        else
            return false;
    }
};
template<typename K, typename V>
class lfu {
private:
    long cur_rount;
    int capacity;
    unordered_map<int, ListNode<K, V>> m;
    set<ListNode<K, V>> freq;
public:
    lfu(int capacity) {
        capacity = capacity;
        cur_rount = 0;
    }
    V get(K key) {
        auto it = m.find(key);
        if (it == m.end())
            return -1;
        V value = it->second.value;
        reinsert(it->second);
        return value;
    }
    void put(K key, V value) {
        if (capacity == 0) return;
        auto it = m.find(key);
        if (it != m.end()) {
            it->second.value = value;
            reinsert(it->second);
            return;
        }
        if (m.size() == capacity) {
            const ListNode<K, V> &node = *freq.begin();
            m.erase(node.key);
            freq.erase(node);
        }
        ListNode<K, V> node{key, value, 1, ++cur_rount};
        m[node.key] = node;
        freq.insert(node);
    }
    void reinsert(ListNode<K, V> &node) {
        freq.erase(node);
        ++node.freq;
        node.cur = ++cur_rount;
        freq.insert(node);
    }
};