vector类接口实现

namespace VECTOR
{
	template<class T>
	class vector
	{
	public:
		typedef T* Iterator;
		typedef const T* ConstIterator;

		Iterator begin()
		{
			return _start;
		}
		Iterator end()
		{
			return _finish;
		}
		ConstIterator cbegin() const
		{
			return _start;
		}
		ConstIterator cend() const
		{
			return _finish;
		}
		size_t size() const
		{
			return _finish - _start;
		}
		size_t capacity() const
		{
			return _endofstorage - _start;
		}
		vector()
			: _start(nullptr)
			, _finish(nullptr)
			,_endofstorage(nullptr)
		{}
		vector(int n, const T& value = T())
			: _start(nullptr)
			, _finish(nullptr)
			,_endofstorage(nullptr)
		{
			reserve(n);
			while(n--)
			{
				push_back(value)
			}
		}
		~vector()
		{
			delete[] _start;
			_start = _finish = _endofstorage = nullptr;
		}
		template<class InputIterator>
		vector(InputIterator first, InputIterator last)
		{
			reserve(last - first);
			while(first++ < last)
			{
				push_back(*first);
			}
		}
		vector(const vector<T>& v)
			: _start(nullptr)
			, _finish(nullptr)
			, _endofstorage(nullptr)
		{
			reserve(v.capacity());
			Iterator it = begin();
			ConstIterator cit = v.cbegin();
			while(cit != cbegin)
			{
				*it++ = *cit++;
			}
			_finish = _start + v.size();
			_endofstorage = _start + v.capacity();
		}
	public:
		void reseve(size_t n)
		{
			if(n > capacity)
			{
				size_t lsize = size();
				T* tmp = new T(n);
				if(_start)
				{
					for(size_t i = 0; i < lsize; ++i)
						tmp[i] = _start[i];

				}
				_start = tmp;
				_finish = _start + tmp;
				_endofstorage = _start + n;
			}
		}
		void swap(vector<T>& v)
		{
			swap(_start, v._start);
			swap(_finish, v._finish);
			sawp(_endofstorage, v._endofstorage);
		}
		void push_back(const T& x)
		{
			insert(_end, x);
		}
		void pop_back()
		{
			erase(_end);
		}
		Iterator insert(Iterator pos, const T& x)
		{
			assert(pos <= _finish && pos >= _start);
			if(finish == _endofstorage)
			{
				size_t lsize = size();
				size_t newcapacity = capacity() == 0 ? 1 : capacity() * 2;
				reserve(newcapcity);
				//增容之后要重置pos
				pos = _start + lsize;
			}
			Iterator end = _finish - 1;
			while(end >= pos)
			{
				*(end+1) = *end;
				--end;
			}
			*pos = x;
			++_finish;
			return pos;
		}
		Iterator erase(Iterator pos)
		{
			assert(pos <= _finish && pos >= _start);
			Iterator begin = pos + 1;
				while(begin != pos+1)
				{
					*(begin-1) = *begin;
					++*begin;
				}
				--_finish;
				return pos;
		}
	private:
		iterator _start;
		iterator _finish;
		iterator _endofstorage;
	};
}