向量（vector容器）

    vector大家都经常使用，其实向量是一个动态数组，所谓动态就是数组在声明后还可以增长，也可以插入元素，动态数组在增长的时候，其实也就是先分配好内存，然后new 一个数组，一个个将原数组再拷贝进去。向量使用完后再delete分配的内存。

    向量的优点和数组一样，缺点就是增长过快的时候比较耗资源。

例子：

数据结构one_vector的简单实现

#include 
     
      using namespace std;template
      
       class  Vector{private:    int theSize;                         //实际数据大小    int theCapacity;                     //实际容器容量大小    Object *objects;                     //基本数组public:    enum { SPACE_CAPACITY = 16 };        //默认容量大小        explicit Vector(int initSize = 0)    //单参数构造函数要用explicit()避免类型在后台转换        : theSize(initSize), theCapacity(initSize + SPACE_CAPACITY) {        objects = new Object[theCapacity];    }    Vector(const Vector& rhs) : objects(NULL) {    //复制构造函数--调用operator=对已有的Vector进行复制        operator = (rhs);    }    ~Vector() {        delete[] objects;    }    const Vector& operator = (const Vector& rhs) //重载赋值运算符    {        if (this != &rhs)                        //避免复制自身--混淆检验        {            delete []objects;                    //删除旧的内存空间            theSize = rhs.size();                //生成同样的样本大小            theCapacity = rhs.theCapacity;       //生成同样的容量大小            objects = new Object[capacity()];    //生成与所复制的Vector同样容量的新数组            for (int k = 0; k < size(); k++)                objects[k] = rhs.objects[k];         }        return *this;    }        void resize(int newSize)    {        if (newSize > theCapacity)        //重置大小            reserve(newSize * 2 + 1);     //新大小        theSize = newSize;    }    void reserve(int newCapacity)    {        if (newCapacity < theSize)        //至少和（样本大小）一样大            return;        Object *oldArray = objects;       //oldArray--用于复制旧数组内容        objects = new Object[newCapacity];        for (int k = 0; k < theSize; k++)            objects[k] = oldArray[k];        theCapacity = newCapacity;        delete []oldArray;    }    Object& operator[] (int index)    {        return objects[index];    }    const Object& operator[] (int index) const    {        return objects[index];    }    bool empty() const {        return size() == 0;    }        int size() const {        return theSize;    }    int capacity() const {        return theCapacity;    }    void push_back(const Object& x) {        if (theSize == theCapacity)            reserve(2 * theCapacity + 1);        objects[theSize++] = x;    }        void pop_back() {        theSize--;    }    const Object& back() const {        return objects[theSize - 1];    }        typedef Object *iterator;    typedef const Object *const_iterator;    iterator begin() {        return &objects[0];    }    const_iterator begin() const {        return &objects[0];    }    iterator end() {               //尾后的不存在的指针        return &objects[size()];         }    const_iterator end() const {        return &objects[size()];    }};int main(){    Vector
       
         test;    int data;    while (cin >> data)    {        test.push_back(data);    }    Vector
        
         ::iterator it;    for (it = test.begin(); it != test.end(); ++it)        cout << *it << " ";    cout << endl;    cout << "pop_one.....\n";    test.pop_back();    cout << test.back() << endl;    return 0;}
        
       
      
     

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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