vector实现（待补充）

template<class T>class vector{public:    //ctor    vector()        : data_(NULL), size_(0)    {    }    explicit vector( size_t n, const T& value = T())    {        data_ = new T[n];        for (size_t i = 0; i < n; i++)        {            data_[0] = value;        }    }    vector<T>& operator=(const vector<T>& rhs)    {        data_ = rhs.data_;        size_ = rhs.size_;    }    //dtor    ~vector()    {        if (data_)        {            delete data_;        }    }    //get    size_t size() const    {        return size_;    }    // set & get    T& operator[](size_t index);    // set    void push_back(const T& element);    void pop_back(const T& element);    void resize();    void reserve();    void clear();    void empty();private:    T*      data_;    size_t  size_;};