MySTL实现之MyVector

MySTL实现之MyVector

MySTL实现

实现STL库中的基础容器及基本函数

文章目录

• MySTL实现
• Vector类实现
• • 头文件.h
  • 测试代码
• 总结

Vector类实现

第一次自己实现模板类，一开始将定义和实现文件分开写，结果vs不能编译。后来发现模板类的实现需要和定义写在一起，因为模板中的T是在编译中才确定的，因此会找不到.cpp的实现文件。

STL中vector类模板的实现还有一个参数是内存分配器，默认是调用系统自带的分配器对内存进行分配，在本次实现中仅采用new关键字对内存进行分配。模板的类型为_T，将 _T*封装为迭代器，用于遍历 _T类型的变量。类中包装3个迭代器作为存取的指示，实现了基本的构造函数、析构函数以及常用函数。

由于有些参数传入需要使用const关键字，因此这些参数在调用其他函数时，也必须调用const关键字修饰的函数。

类中没有实现例如：

vector vec(10);
vec[0] = 0;

这种赋值形式，只能使用push_back()在vector尾部添加，或insert(it,val)在it位加入val，但每次仅能插入一个。

最后给出简单测试代码，对于一些细节的把控可能还没完善。

头文件.h

#pragma once
#ifndef _MyVector_
#define _MyVector_
#include<iostream>
template<class _T>
class MyVector {
private:_T* _my_first;//起始位置_T* _my_finish;//最后一个存入元素的后一个_T* _my_end;//最大容量的后一个public:typedef _T* iterator;//迭代器//默认构造MyVector() :_my_first(nullptr), _my_finish(nullptr), _my_end(nullptr) {}/// <summary>/// 有参构造函数/// </summary>/// <param name="n">长度</param>/// <param name="val">初始值</param>MyVector(size_t n, const _T& val = _T()) :_my_first(nullptr), _my_finish(nullptr), _my_end(nullptr) {//重新申请空间_my_first = new _T[n];_my_finish = _my_first;_my_end = _my_first + n;//赋值for (auto it = begin(); it != _my_end; ++it) {*_my_finish = val;++_my_finish;}_my_finish = _my_first;//赋完初值后，指针归位}/// <summary>/// 复制构造函数/// </summary>/// <typeparam name="_T"></typeparam>/// <param name="v"></param>MyVector(const MyVector& v) {//得到v的容量size_t n = v.capacity();//重新申请空间_my_first = new _T[n];_my_finish = _my_first;_my_end = _my_first + n;//赋值//传入的v为const，对应取出的begin也要为constfor (auto it = v.begin(); it != v.end(); ++it) {*_my_finish = *it;++_my_finish;}}/// <summary>/// 析构函数/// 是否应该显式调用数组中每个对象的析构函数？/// </summary>/// <typeparam name="_T"></typeparam>~MyVector() {if (_my_first) {delete[] _my_first;_my_first = _my_finish = _my_end = nullptr;}}//返回迭代器iterator begin() {return _my_first;}iterator end() {return _my_finish;}//返回常量迭代器iterator begin() const {return _my_first;}iterator end() const {return _my_finish;}/// <summary>/// 压入myvector/// </summary>/// <typeparam name="_T"></typeparam>/// <param name="val"></param>void push_back(const _T& val) {if (end() == _my_end) {//空间不足this->insert(end(), val);}else {//有空间，直接存this->construction(end(), val);_my_finish++;}}/// <summary>/// 在迭代器位置加入n个该元素,默认个数为1/// </summary>/// <param name="v"></param>void construction(iterator cur, const _T& val, int n = 1) {for (int i = 0; i < n; ++i) {*cur = val;cur++;}}/// <summary>/// 弹出myvector/// </summary>/// <typeparam name="_T"></typeparam>void pop_back() {this->erase(end());}//获取sizesize_t size() {return size_t(end() - begin());}size_t capacity() {return _my_first == nullptr ? 0 : _my_end - _my_first;}size_t capacity() const {return _my_first == nullptr ? 0 : _my_end - _my_first;}/// <summary>/// 在MyVector插入val/// 1、空间不足/// 2、直接插入/// </summary>/// <typeparam name="_T"></typeparam>/// <param name="pos">插入位置</param>/// <param name="val">插入值</param>void insert(iterator pos, const _T& val) {size_t posindex = pos - _my_first;if (_my_finish == _my_end){//空间不足size_t newcapacity = capacity() == 0 ? 2 : capacity() * 2;resize(newcapacity);//重新申请大小pos = _my_first + posindex;}//后移iterator end = _my_finish;while (end > pos){*end = *(end - 1);--end;}*pos = val;++_my_finish;}/// <summary>/// 移除pos位的元素/// 后面整体前移一位/// finish前移一位/// </summary>/// <typeparam name="_T"></typeparam>/// <param name="pos"></param>/// <returns></returns>iterator erase(iterator pos) {iterator begin = pos;for (iterator it = pos; it != end(); ++it) {*it = *(it + 1);}--_my_finish;return begin;}/// <summary>/// 重新申请空间/// 1.缩容			1）对象在新空间存满  2）对象在新空间只存了一部分/// 2.扩容/// </summary>/// <typeparam name="_T"></typeparam>/// <param name="n"></param>void resize(size_t n) {if (n < capacity()) {	//缩容_T* new_data = new _T[n];_T* new_fir = new_data;//赋值for (auto it = begin(); it != begin() + n && it != end(); ++it) {*(new_data++) = *it;}size_t old_size = size() < n ? size() : n;delete[] _my_first;//删除原先数据_my_first = new_fir;_my_finish = begin() + old_size;_my_end = begin() + n;}else if (n > capacity()) {	//扩容_T* new_data = new _T[n];_T* new_fir = new_data;for (auto it = begin(); it != end(); ++it) {*(new_data++) = *it;}size_t old_size = size();delete[] _my_first;//删除原先数据_my_first = new_fir;_my_finish = _my_first + old_size;_my_end = _my_first + n;}}/// <summary>/// 重载[]/// </summary>/// <typeparam name="_T"></typeparam>/// <param name="n"></param>/// <returns></returns>_T& operator[](size_t n) {return *(_my_first + n);}/// <summary>/// 重载=/// </summary>/// <typeparam name="_T"></typeparam>/// <param name="v"></param>/// <returns></returns>MyVector<_T>& operator=(const MyVector<_T>& v) {//得到v的容量size_t n = v.capacity();//重新申请空间_my_first = new _T[n];_my_finish = _my_first;_my_end = _my_first + n;//赋值for (auto it = v.begin(); it != v.end(); ++it) {*_my_finish = *it;++_my_finish;}return this;}bool empty() const {return end() == begin();}
};
#endif // !_MyVector_

测试代码

没有实现对于越界等问题的异常处理

#include"MyVector.h"
#include<iostream>
#include<algorithm>
int main() {//测试默认构造函数MyVector<int> vec1;vec1.push_back(0);vec1.push_back(1);vec1.push_back(2);vec1.push_back(3);vec1.push_back(4);vec1.push_back(5);std::cout << "vec1:" << std::endl;for (auto it = vec1.begin(); it != d(); ++it) {std::cout << *it << std::endl;}std::cout << "vec2:" << std::endl;//测试有参构造MyVector<int> vec2(5);for (int i = 0; i < 5; i++) {vec2.insert(vec2.begin(), i);}for (auto it = vec2.begin(); it != d(); ++it) {std::cout << *it << std::endl;}//测试赋值构造MyVector<int>vec3(vec2);std::cout << "vec3:" << std::endl;for (auto it = vec3.begin(); it != d(); ++it) {std::cout << *it << std::endl;}MyVector<int> vec4 = vec3;vec4.pop_back();vec4.pop_back();ase(vec4.begin() + 1);std::cout << "vec4:" << std::endl;for (auto it = vec4.begin(); it != d(); ++it) {std::cout << *it << std::endl;}std::cout << "vec4.size():" << vec4.size() << std::endl;//测试size(3);std::cout << "vec1:" << std::endl;for (auto it = vec1.begin(); it != d(); ++it) {std::cout << *it << std::endl;}size(10);for (int i = 2; i < 10; i++) {vec4.push_back(i);}std::cout << "vec4.size():" << vec4.size() << std::endl;vec4.insert(vec4.begin() + 5, 10);std::cout << "vec4.size():" << vec4.size() << std::endl;std::cout << "vec4:" << std::endl;for (auto it = vec4.begin(); it != d(); ++it) {std::cout << *it << std::endl;}if (pty()) {std::cout << "vec1为空" << std::endl;}else {std::cout << "vec1不空" << std::endl;}//测试能否适配算法库std::sort(vec4.begin(), d());std::cout << "vec4:" << std::endl;for (auto it = vec4.begin(); it != d(); ++it) {std::cout << *it << std::endl;}return 0;
}

总结

简单实现了一遍vector，包装了3个指针对一块连续内存空间的操作，对于更深层次的内存分配器还没有进一步实现，本次实现中仅使用new关键字对内存空间进行分配。
接下来会实现list容器及相关函数，MyVector类文件在该仓库（如果对你有帮助或者你发现了问题都可以在仓库点赞或提交问题）也可以从这里下载。