【STL】vector的模拟实现

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STL中的vector也是一个常用的容器，他是一个顺序表，很多用法和接口都和list的一样。

下面来看一下vector的模拟实现

#include #include using namespace std;templateclass Vector{public:typedef  T* Iterator;typedef const T* ConstIterator;Vector()  //空参数的构造函数:_start(NULL), _finish(NULL), _EndofStore(NULL){}Vector(size_t n, T val)   //参数为n个value的构造:_start(new T[n]), _finish(_start), _EndofStore(_start+n)   {size_t i = 0;for (i = 0; i < n;i++){_start[i] = val;}_finish = _start + n;    }Vector(const Vector & v)   //参数为Vector的拷贝构造:_start(NULL), _finish(NULL), _EndofStore(NULL){size_t size = v.Size();if (size > 0){Expand(size);for (size_t i = 0; i < size; i++){_start[i] = v._start[i];}_finish = _start + size;}}Vector(ConstIterator first, ConstIterator last)     //参数为迭代器区间的构造:_start(NULL), _finish(NULL), _EndofStore(NULL){size_t size = first - last;if (size > 0){Expand(size);for (size_t i = 0; i < size; i++){_start[i] = first[i];}_finish = _start + size;}}~Vector()   //析构函数{Destroy();}bool Checkfull(){return _EndofStore >= _finish;}void Expand(size_t n)   //增容函数{assert(n > Capacity());T* tmp = new T[n];size_t size = Size();for (size_t i = 0; i < size; i++)    //扩容后拷贝原来数据{tmp[i] = _start[i];}delete[] _start;_start = tmp;_finish = _start + size;_EndofStore = _start + n;}void Destroy()       //销毁Vector的函数{if (_start != NULL){delete[] _start;}_start = _finish = _EndofStore = NULL;}size_t Size()const{return _finish - _start;}size_t Capacity()const{return _EndofStore - _start;}//迭代器的生成器Iterator Begin(){return _start;}Iterator End(){return _finish;}void CheckCapacity(){if (_finish == _EndofStore){size_t newcapacity = Capacity() + 3;Expand(newcapacity);}}void Insert(Iterator pos, const T& x)  //随机位置的插入函数，尾插头插都靠他{size_t newpos = pos - _start;          //因为要调整空间，旧的pos在调整空间以后会失效，先记录与_start的偏移量；在调整后的新空间能找到对应的新posCheckCapacity();pos = _start + newpos;for (Iterator tmp = End(); tmp > pos; tmp--){*tmp = *(tmp - 1);}*pos = x;_finish++;}void Erase(Iterator &pos)  //任意位置的删除函数，尾删头删都靠他{Iterator end = End();for  (; pos < (--end); pos++){*pos = *(pos + 1);}_finish--;}void Pushback(const T& val)   //尾插{Insert(End(), val);}void Popback()   //尾删{if (Size() != 0){Iterator end= End();Erase( --end );}}void Pushfront(const T& val) //头插{Insert(Begin() , val);}void Popfront()  //头删{if (Size() != 0){Iterator start= Begin();Erase(start);}}protected:Iterator _start;Iterator _finish;Iterator _EndofStore;};

特别要注意的是增容；一旦在insert收到pos参数后再增容就会关系到原来传入pos失效的问题。我使用了pos与老的_start的偏移量来解决的；

或者可以：在传入insert参数pos之前，就增好容量，而int内部不增容的方案。我的是前者。

测试代码：

template<class T>void PrintVector(Vector<T>& v){size_t size = v.Size();Vector<T>::ConstIterator it = v.Begin();if (size != 0){for (size_t i = 0; i < size; i++){cout << it[i] << " ";}cout << endl;}}void construct_test(){Vector<int> v1;Vector<int> v2(3, 4);Vector<int> v3(v2);Vector<string>v4(3, "hello   ");Vector<int>::Iterator it = v2.Begin();PrintVector<int>(v1);PrintVector<int>(v2);PrintVector<int>(v3);}void ModifiersTest(){Vector<int> v1(1,1);v1.Pushback(2);v1.Pushback(3);v1.Pushback(4);v1.Pushback(5);v1.Pushfront(0);v1.Popback();v1.Popback();v1.Popback();v1.Popback(); v1.Popfront();v1.Popfront();v1.Popfront();PrintVector<int>(v1);}

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