迭代器实现Vector

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vector模型是一个动态数组，它本身是“将元素至于动态数组中加以管理”的一个抽象概念，但是c++标准并未要求以动态数组实作vector。
在使用标准库里面的vector时，必须包含头文件#include<vector> 其中型别vector是一个定义于namespace std的template。

namespace std{  template<class T,class Allocator =allocator<T>>  class vector;}

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通过查看标准库里面的vector函数，利用迭代器Iterator，模拟实现vector，代码如下：

#define _CRT_SECURE_NO_WARNINGS 1#include<iostream>#include<vector>#include<assert.h>using namespace std;template<typename T>class Vector{public:    typedef T* Iterator;    Vector()        :_start(0)        , _finish(0)        , _endOfstorage(0)    {}    Vector(const T* str, size_t size)//构造size个元素        :_start(new T[size])        , _finish(_start)//（没放空间时）//_finish(_start+size)（放了空间）        , _endOfstorage(_start + size)    {        //memcpy(_start,str,sizeof(T)*size);        for (size_t i = 0; i<size; ++i)        {            *_finish++ = str[i];//_start[i]=str[i];        }    }    Vector(const Vector<T>& v)//拷贝构造函数    {        size_t size = Size();        _start = new T[size];        for (size_t i = 0; i<size; i++)        {            _start[i] = v._start[i];        }        _finish = _start + size;        _endOfstroage = _finish;    }    Vector& operator=(const Vector<T>& v)//赋值运算符重载    {        size_t size = v.Size();        if (this != &v)        {            T*tmp = new T[size];            for (size_t i = 0; i<size; i++)//深拷贝            {                tmp[i] = _start[i];            }            delete[] _start;            _start = tmp;            _finish = _start + size;            _endOfstorge = _finish;        }        return *this;    }    ~Vector()    {        if (_start)        {            delete[] _start;            _start = NULL;        }    }    //////////////////////Iterator////////////////////////////      Iterator Begin()    //迭代器      {        return _start; //Begin和_start类型一致     }    Iterator End()    {        return _finish;    }    ///////////////////Modify////////////////////////////////     void PushBack(const T& data)    {        CheckCapacity();        *_finish = data;        ++_finish;    }    void PopBack()    {        --_finish;    }    void Insert(size_t pos, const T& data)    {        size_t size = Size();        CheckCapacity();        assert(pos<size);        for (size_t i = size; i>pos; --i)        {            _start[i] = _start[i - 1];        }        _start[pos] = data;        ++_finish;    }    void Erase(size_t pos)    {        size_t size = Size();        assert(pos<size)        for (size_t i = pos; i<size; i++)        {            _start[i] = start[i + 1];        }        --_finish;    }    //////////////////capacity////////////////////////////     size_t Size()const    {        return _finish - _start;    }    size_t CapaCity()const    {        return _endOfstorage - _start;    }    bool Empty()const//判空    {        if (_atart == _finish)        {            return true;        }        return false;    }    void Resize(size_t newSize, const T& data = T())//改变大小    {        size_t size = Size();//原来元素大小        size_t capacity = CapaCity();//原来容量        //1.newSize比size小        if (newSize<size)        {            _finish == _start + newSize;        }        //2.newSize比size大，但比capacity小        else if (newSize>size&&newSize<capacity)        {            for (size_t i = size; i<newSize; i++)            {                //*finish++=data;                _start[i] = data;            }            _finish = _start + newSize;        }        //newSize比capacity大        else        {            T* tmp = new T[newSize];//开辟新空间            for (size_t i = 0; i<size; i++)//搬移原空间的元素            {                tmp[i] = _start[i];            }            for (size_t i = size; i<newSize; i++)//把新增加的元素加进来            {                tmp[i] = data;            }            delete[] _start;//释放旧空间            _start = tmp;            _finish = _start + newSize;            _endOfstorage = _finish;        }    }    //////////////Element Acess(元素访问)///////////////////////////     T& operator[](size_t index)//随机访问（下标）    {        size_t capacity = CapaCity();        assert(index <= capacity);        return _start[index];    }    const T& operator[](size_t index)const    {        size_t capacity = CapaCity();        assert(index <= capacity);        return _start[index];    }    T& Front()    {        return *_start;    }    const T& Front()const    {        return *_start;    }    T& Back()    {        return *(_finish - 1);    }    const T& Back()const    {        return *(_finish - 1);    }    void Clear()    {        _finish = _start;    }    friend ostream& operator<<(ostream& os, const Vector<T>& v)    {        for (size_t i = 0; i<v.Size(); i++)        {            os << v[i] << " ";        }        os << endl;        return os;    }    /*friend ostream& operator<<(ostream& os,  Vector<T>* v)//通过迭代器重载    {        Vector<int>::Iterator it = v.Begin();            while(it!=v.End())            {                cout<<*it<<" ";                ++it;            }            os << endl;            return os;    }*/private:    void CheckCapacity()    {        size_t size = Size();        size_t capacity = CapaCity();        size_t newcapacity = 2 * capacity + 2;        if (size >= capacity)        {            //增容            T* tmp = new T[newcapacity];            //拷贝元素            //if(_start)            //memcpy(tmp,_start,size*sizeof(T));//浅拷贝（导致两个字符串公用同一块空间）但是效率高            //出了函数作用域，要销毁v，销毁旧空间时出现问题            for (size_t i = 0; i<size; i++)            {                tmp[i] = _start[i];            }            delete[] _start;//释放旧空间            _start = tmp;            _finish = _start + size;            _endOfstorage = _start + newcapacity;        }    }private:    T* _start;    T* _finish;    T* _endOfstorage;};void TestVector()//测试函数{    int arr[]={1,2,3,4};    Vector<int>v(arr,sizeof(arr)/sizeof(arr[0]));    cout<<"Size="<<v.Size()<<endl;    cout<<"Capacity="<<v.CapaCity()<<endl;    cout<<v<<endl;    Vector<int>::Iterator it=v.Begin();    while(it!=v.End())    {        cout<<*it<<" ";        ++it;    }    cout<<endl;    v.PushBack(5);    cout << v << endl;    v.Insert(0, 0);    cout << v << endl;    v.Resize(20);    cout << "Size=" << v.Size() << endl;    cout << "Capacity=" << v.CapaCity() << endl;    v.Clear();    cout << "Size=" << v.Size() << endl;    cout << "Capacity=" << v.CapaCity() << endl;}int main(){    TestVector();    system("pause");    return 0;}

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