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实现自己的一个Vector类
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//vector.h #include<iostream> #include<string> using namespace std; template<typename T> class vector { class proxy; public: vector(); ~vector(); void push_back(const T&); void pop_back(); proxy operator[](int index); int size(); int capacity(); void reallocate(); // 重新分配内存，动态扩容 private: T* _elems; // 指向数组中的第一个元素 T* _end; // 指向数组本身之后的元素 T* _first_free; // 指向最后一个实际元素之后的那个元素 class proxy { public: proxy(vector<T>& v,int index):_v(v),_index(index){} // 这里形参一定要是引用，传本身啊，不然最后_v._elems[_index]就是错的。浅拷贝 T& operator=(const int elem); operator T(){ return _v._elems[_index]; } private: vector<T>& _v; // 这个地方也是引用 int _index; }; }; // Vector模型 // ______________________________ // |_|_|_|_|_|____________________| // ↑ ↑ ↑ // _elems _first_free _end //main.cpp #include<iostream> #include"vector.cpp" using namespace std; int main() { vector<int> v1; cout<<v1.size()<<" "<<v1.capacity()<<endl; v1.push_back(1); cout<<v1.size()<<" "<<v1.capacity()<<endl; v1.push_back(2); cout<<v1.size()<<" "<<v1.capacity()<<endl; v1.push_back(3); cout<<v1.size()<<" "<<v1.capacity()<<endl; v1.pop_back(); cout<<v1.size()<<" "<<v1.capacity()<<endl; v1.pop_back(); cout<<v1.size()<<" "<<v1.capacity()<<endl; cout<<"----------------------------------"<<endl; cout<<"v1[0]="<<v1[0]<<endl; //v1[0] = 2; //(v1[0]).operator=(2); (v1.operator[](0)).operator=(2); cout<<"after change:"<<endl; cout<<"v1[0]="<<v1[0]<<endl; return 0; } |
//vector.cpp #include<iostream> #include"vector.h" #include<string.h> using namespace std; template<typename T> vector<T>::vector():_elems(new T[1]),_first_free(_elems) { T* tmp = _elems; _end = ++tmp; } template<typename T> vector<T>::~vector() { delete _elems; _elems = NULL; } template<typename T> int vector<T>::size() { return _first_free-_elems; } template<typename T> int vector<T>::capacity() { return _end-_elems; } template<typename T> void vector<T>::reallocate() { int size = this->size(); T* tmp = new T[size*2]; memcpy(tmp,_elems,size*sizeof(T)); _elems = tmp; _first_free = _elems+size; _end = (_elems+size*2); } template<typename T> void vector<T>::push_back(const T& elem) { if(this->size()!=this->capacity()) { int i = (_first_free-_elems)/sizeof(T); _elems[i] = elem; ++_first_free; } else if(this->size()==this->capacity()) { this->reallocate(); int i = (_first_free-_elems)/sizeof(T); _elems[i] = elem; ++_first_free; } } template<typename T> void vector<T>::pop_back() { if(this->size()!=0) --_first_free; } template<typename T> typename vector<T>::proxy vector<T>::operator[](int index) { return proxy(*this,index); // 嵌套类不传引用这里出作用域释放了，后面的=什么的没错误，但是执行就报错 } template<typename T> T& vector<T>::proxy::operator=(const int elem) { _v._elems[_index] = elem; return _v._elems[_index]; } |
原文地址：https://www.cnblogs.com/meihao1203/p/9049225.html