非排序map的适配器

以前写过的一些代码，拿出来与大家分享一下，在看代码前先交代清楚它的优缺点，顾名思义此适配器去除了std::map按key排序的特性，元素的排序按我们插入的顺序排列，因此失去了二分查找的性能，查询的时间为常数N。在我们不希望std::map排序元素，且保存元素较少的情况下，这是个不错的解决方案。

Map.h

#pragma once#include <vector>#include <utility>namespace std{template<class K,class V,class A = allocator< pair<K, V> >>class Map : private vector< pair<K, V>, A >{typedef vector<pair<K, V>, A> Base;public:typedef K key_type;typedef V mapped_type;typedef typename Base::value_type value_type;typedef typename Base::iterator iterator;typedef typename Base::const_iterator const_iterator;typedef typename Base::size_type size_type;typedef typename Base::reverse_iterator reverse_iterator;typedef typename Base::const_reverse_iterator const_reverse_iterator;explicit Map(const A& alloc = A()): Base(alloc){}template <class InputIterator>Map(InputIterator first, InputIterator last, const A& alloc = A()): Base(first, last, alloc){}Map& operator=(const Map& rhs){ Map(rhs).swap(*this); return *this;}iterator begin() { return Base::begin(); }const_iterator begin() const { return Base::begin(); }iterator end() { return Base::end(); }const_iterator end() const { return Base::end(); }reverse_iterator rbegin() { return Base::rbegin(); }const_reverse_iterator rbegin() const { return Base::rbegin(); }reverse_iterator rend() { return Base::rend(); }const_reverse_iterator rend() const { return Base::rend(); }bool empty() const { return Base::empty(); }size_type size() const { return Base::size(); }size_type max_size() { return Base::max_size(); }mapped_type& operator[](const key_type& key){ if (find(key) != end()){return find(key)->second;}else{push_back(value_type(key,mapped_type()));return find(key)->second;}}void insert(const value_type& val){Base::push_back(val);}iterator insert(iterator pos, const value_type& val){return Base::insert(pos, val);}template <class InputIterator>void insert(InputIterator first, InputIterator last){ for (; first != last; ++first) insert(*first); }void erase(iterator pos){ Base::erase(pos); }size_type erase(const key_type& k){iterator i(find(k));if (i == end()) return 0;erase(i);return 1;}void erase(iterator first, iterator last){ Base::erase(first, last); }void swap(Map& other){Base::swap(other);}void clear(){ Base::clear(); }iterator find(const key_type& k){iterator i(Base::begin());for (;i!=Base::end();++i){if(i->first == k)return i;}return i;}const_iterator find(const key_type& k) const{       const_iterator i(Base::begin());for (;i!=Base::end();++i){if(i->first == k)return i;}return i;}size_type count(const key_type& k) const{ size_type i = 0;for (const_iterator i = Base::begin();i!=Base::end();++i){if (i->first == k){++i;}}return i;}};} 

main.cpp //对比std::map

#include "Map.h"#include <iostream>#include <string>#include <map>using namespace std;int main(void){    Map<int,string> strs_M;    strs_M[4] = "four";    strs_M[3] = "three";    strs_M[5] = "five";    strs_M[7] = "seven";    strs_M[2] = "two";    strs_M[1] = "one";    strs_M[0] = "zero";    for(Map<int,string>::iterator it = strs_M.begin();        it != strs_M.end();++it)        cout<<it->first<<" "<<it->second<<endl;    cout<<"==============================================="<<endl;    map<int,string> strs_m;    strs_m[4] = "four";    strs_m[3] = "three";    strs_m[5] = "five";    strs_m[7] = "seven";    strs_m[2] = "two";    strs_m[1] = "one";    strs_m[0] = "zero";    for(map<int,string>::iterator it = strs_m.begin();        it != strs_m.end();++it)        cout<<it->first<<" "<<it->second<<endl;    return 0;}