#ifndef VECTOR_H_
#define VECTOR_H_#include <stddef.h>
#include <algorithm>
#include <memory>template <typename T>
class Vector
{
public:typedef T *iterator;typedef const T *const_iterator;typedef size_t size_type;typedef T value_type;Vector() { create(); }explicit Vector(size_type n, const T &t = T())  { create(n, t); }Vector(const Vector &v) { create(v.begin(),  v.end()); }~Vector() { uncreate(); }Vector &operator=(const Vector &other);T &operator[] (size_type i) { return data_[i]; }const T &operator[] (size_type i) const { return data_[i]; }void push_back(const T &t);size_type size() const { return avail_ - data_; }size_type capacity() const { return limit_ - data_; }iterator begin() { return data_; }const_iterator begin() const { return data_; }iterator end() { return avail_; }const_iterator end() const { return avail_; }private:iterator data_; //首元素iterator avail_; //末尾元素的下一个位置iterator limit_; //内存的后面一个位置
std::allocator<T> alloc_; //内存分配器void create();void create(size_type, const T &);void create(const_iterator, const_iterator);void uncreate();void grow();void uncheckedAppend(const T &);
};template <typename T>
Vector<T> &Vector<T>::operator=(const Vector &rhs)
{if(this != &rhs){uncreate(); //释放原来的内存
        create(rhs.begin(), rhs.end());}return *this;
}template <typename T>
void Vector<T>::push_back(const T &t)
{if(avail_ == limit_){grow();}uncheckedAppend(t);
}template <typename T>
void Vector<T>::create()
{//分配空的数组data_ = avail_ = limit_ = 0;
}template <typename T>
void Vector<T>::create(size_type n, const T &val)
{//分配原始内存data_ = alloc_.allocate(n);limit_ = avail_ = data_ + n;//向原始内存填充元素
    std::uninitialized_fill(data_, limit_, val);
}template <typename T>
void Vector<T>::create(const_iterator i, const_iterator j)
{data_ = alloc_.allocate(j-i);limit_ = avail_ = std::uninitialized_copy(i, j, data_);
}template <typename T>
void Vector<T>::uncreate()
{if(data_){//逐个进行析构iterator it = avail_;while(it != data_){alloc_.destroy(--it);}//真正的释放内存alloc_.deallocate(data_, limit_ - data_);}//重置指针data_ = limit_ = avail_ = 0;
}template <typename T>
void Vector<T>::grow()
{//内存变为两倍size_type new_size = std::max(2 * (limit_ - data_), std::ptrdiff_t(1));//分配原始内存iterator new_data = alloc_.allocate(new_size);//复制元素iterator new_avail = std::uninitialized_copy(data_, avail_, new_data);uncreate(); //释放以前的内存，以及析构元素
data_ = new_data;avail_ = new_avail;limit_ = data_ + new_size;
}template <typename T>
void Vector<T>::uncheckedAppend(const T &val)
{alloc_.construct(avail_++, val);
}#endif  /* VECTOR_H_ */

#include "Vector.hpp"
#include <iostream>
#include <string>
using namespace std;int main(int argc, char const *argv[])
{Vector<string> vec(3, "hello");for(Vector<string>::const_iterator it = vec.begin();it != vec.end();++it){cout << *it << " ";}cout << endl;cout << "size = " << vec.size() << endl;cout << "capacity = " << vec.capacity() << endl;vec.push_back("foo");vec.push_back("bar");cout << "size = " << vec.size() << endl;cout << "capacity = " << vec.capacity() << endl;return 0;
}