c++vector简单实现

const  int DEFAULT_CAP = 3;

template 
class vector {
    //
    int capacity;
    T* _data;
    int _size;
    
public:
    //const
    vector ():capacity(DEFAULT_CAP),_size(0),_data(new T[capacity]){};
    
    vector(vector& v):capacity(v.cap()),_size(v.size()),_data(new T[capacity]) {
        memcpy(_data, v._data, _size*sizeof(T));
    }
    vector(vector&& v):capacity(v.cap()),_size(v.size()) {
        _size = v.getdata();
        v._data = nullptr;
    }
    //deconst
    virtual ~vector(){ delete [] _data;}
    //operator
    vector& operator=(const vector &v) {
        /*
        if(this != &v){
            delete [] _data;
            _size = v.size();
            capacity = v.cap();
            _data = new T[capacity];
            memcpy(_data, v._data, _size*sizeof(T));
        }*/
        sw(v);
        return *this;
    }
    T& operator[](int i) const{
        return _data[i];
    }
    //retrun
    int size() const {return _size;}
    int cap() const {return capacity;}
    const int getdata() const noexcept {_data;}
    //function
    void expand() {
        if(_size == capacity){
            capacity = capacity<<1;
        T *old = _data;
        _data = new T[capacity];
        memcpy(_data, old, _size*sizeof(T));
        delete [] old;
        }
    }
    void push_back(T const& temp) {
        expand();
        _data[_size++] = temp;
    }
    void each(){
        for (int i = 0; i < _size; ++i) {
            cout<<_data[i]<