简洁高效的LRU Map C++实现

1: #include <map>

   2: #include <string>

   3: #include <iostream>

using namespace std;

   5:  

   6:  template<class K, class V>

public map<K, V> 

   8:  {

   9:      typedef map<K, V> base_type;

timestamp;

timestamp> K2T;

timestamp, K> T2K;

  13:   

// from key to timestamp

// from timestamp to key

  16:   

timestamp tm;

  18:      size_type capacity;

  19:      lrumap(size_type cap=10)

  20:          : tm(1), capacity(cap) {}

  21:   

  22:      V& operator[](const K& k)

  23:      {

timestamp& _tm=k2t[k];

// if the timestamp already exist, delete it from t2k

  26:              t2k.erase(_tm);

// update timestamp in k2t

// update key in t2k

  29:   

  30:          V& ret= base_type::operator[](k);

  31:   

// remove the oldest if necessary

  33:          if(size()>capacity)

  34:          {

// get the eldest key

  36:              erase(k);

  37:          }

  38:          return ret;

  39:      }

  40:      void erase(const K& k)

  41:      {

// erase timestamp <-> key reference

  43:          t2k.erase(k2t[k]);

  44:          k2t.erase(k);

// then the actual data

  46:          base_type::erase(k);

  47:      }

  48:  };