C++vector模拟实现

vector.h

#pragma once
#include<assert.h>
#include<iostream>

namespace dk
{
	template<class T>
	class vector
	{

	public:
		//迭代器
		typedef T* iterator;
		typedef const T*  const_iterator;

		iterator begin()
		{
			return _start;
		}
		iterator end()
		{
			return _finish;
		}
		const_iterator begin() const
		{
			return _start;
		}
		const_iterator end() const
		{
			return _finish;
		}
		//构造函数  析构函数
		vector()
			:_start(nullptr)
			, _finish(nullptr)
			, _endofstorage(nullptr)
		{}
		template<class InputIterator>
		vector(InputIterator first, InputIterator last)
			: _start(nullptr)
			, _finish(nullptr)
			, _endofstorage(nullptr)
		{
			reserve(last - first);
			while (first != last)
			{
				push_back(*first);
				++first;
			}
		}
		void swap(vector<T>& v)
		{
			std::swap(_start, v._start);
			std::swap(_finish, v._finish);
			std::swap(_endofstorage, v._endofstorage);
		}
		//v1(v2)拷贝构造 深拷贝
		vector(const vector<T>& v)
			: _start(nullptr)
			, _finish(nullptr)
			, _endofstorage(nullptr)
		{
			vector<T> tmp(v.begin(), v.end());
			// v是对v2的引用，创建tmp后，开辟空间对v的
			//内容进行拷贝，最后交换this（v1的引用）和tmp
			//完成拷贝构造
			this->swap(tmp);
		}
		//v1 = v2
		vector<T>& operator = (vector<T> v)//v是对v2的拷贝
			//所以直接交换，返回*this是v1
		{
			this->swap(v);
			return *this;
		}
		~vector()
		{
			delete[] _start;
			_start = _finish = _endofstorage = nullptr;
		}
		// capcacity
		size_t capacity()
		{
			return _endofstorage - _start;
		}
		size_t size()
		{
			return _finish - _start;
		}

		T& operator[] (size_t pos)
		{
			assert(pos < size());
			return _start[pos];//_start 类似于string中的_str ,char*的指针
		}
		//扩容
		void reserve(size_t n)
		{
			if (n > capacity())
			{
				size_t sz = size();
				T* tmp = new T[n];
				//int char 内置类型 调memcpy
				//自定义类型如（string）用  for + operator=
				//memcpy(tmp, _start, sizeof(T)*size());
				for (size_t i = 0; i < sz; ++i)
				{
					tmp[i] = _start[i];
				}
				delete[] _start;
				_start = tmp;

				_finish = _start + sz;
				_endofstorage = _start + n;
			}

		}
		void resize(size_t n, const T& val = T())
		{
			if (n > capacity())
			{
				reserve(n);
			}
			if (n < size())
			{
				_finish = _start + n;
			}
			else
			{
				while (_finish != _start + n)
				{
					*_finish = val;
					++_finish;
				}
			}
		}
		void check_capacity()//判断容量是否够，不够则扩容
		{
			if (_finish == _endofstorage)
			{
				size_t newcapacity = capacity() == 0 ? 4 : capacity() * 2;
				reserve(newcapacity);
			}
		}
		//尾插
		void push_back(const T& x)
		{
			check_capacity();

			*_finish = x;
			++_finish;
		}
		//尾删
		void pop_back()
		{
			assert(_finish > _start);
			--_finish;
		}
		//任意位置插入
		//insert这里pos是实参的拷贝，insert内部pos改变，不能引起
		//实参的改变，所以给一个返回值，解决迭代器失效的问题
		/*void */iterator insert(iterator pos, const T& x)
		{
			assert(pos >= _start && pos <= _finish);
			size_t posi = pos - _start;

			//check_capacity后，若需要增容，则调用reserve
			//此时开辟了一个新的空间，pos还留在原来的空间
			//所以pos = posi + _start;找到新空间的pos位置
			check_capacity();
			pos = posi + _start;

			iterator end = _finish - 1;
			while (end >= pos)
			{
				*(end - 1) = *end;
				--end;
			}
			*pos = x;
			--end;
			return pos;//返回值可以解决迭代器失效
		}

		iterator erase(iterator pos)
		{
			assert(pos >= _start && pos < _finish);

			iterator it = pos + 1;
			while (it != _finish)
			{
				*(it - 1) = *it;
				++it;
			}
			--_finish;

			return pos;
		}
	private:
		iterator _start;//指向数据块的开始
		iterator _finish;//指向有效数据的尾
		iterator _endofstorage;//指向存储容量的尾
	};
}

test.c

#include<iostream>
#include<vector>
#include<string>
using namespace std;

#include"vector.h"

//void test_vector1()
//{
//	dk::vector<int>v;
//	v.push_back(1);
//	v.push_back(2);
//	v.push_back(3);
//	v.push_back(4);
//	v.push_back(5);
//
//	for (size_t i = 0; i < v.size(); ++i)
//	{
//		v[i] *= 2;
//		cout << v[i] << " ";
//	}
//	cout << endl;
//	for (auto e : v)
//	{
//		cout << e << " ";
//	}
//	cout << endl;
//}

void test_vector2()
{
	dk::vector<string> v;
	v.push_back("1111");
	v.push_back("1111");
	v.push_back("1111");
	v.push_back("1111");
	v.push_back("1111");

	for (const auto& e : v)
	{
		cout << e << " ";
	}
	cout << endl;
}

int main()
{

	test_vector2();
	return 0;
}