【C++】vector的模拟实现

vector的模拟实现

• 模拟标准库中的·vector

代码

my_vector.h

#pragma once

#include <iostream>
#include <assert.h>
using namespace std;



namespace my_vector
{
	template<class T>
	class vector
	{
	public:
		typedef T* iterator;
		typedef T* const_iterator;
		vector()
		{}
		~vector()
		{
			delete[] _start;
			_start = _finish=_endofstorage = nullptr;
		}
		vector(const vector<T>& x)
		{
			reserve(x.capacity());
			for (auto& e : x)
			{
				push_back(e);
			}
		}
		//vector<int> v = {1,2,3,4,5,6,7,8,9}
		vector(initializer_list<T>il)
		{
			reserve(il.size());
			for (auto& e : il)
			{
				push_back(e);
			}
		}
		template <class InoutIterator>
		vector(InoutIterator first, InoutIterator last)
		{
			while (first != last)
			{
				push_back(*first);
				++first;
			}
		}

		vector(size_t n, const T& val = T())
		{
			reserve(n);
			for (size_t i = 0; i < n; i++)
			{
				push_back(val);
			}
		}
		//防止 vector<int>v(10,1)  时冲突
		vector(int n, const T& val = T())
		{
			reserve(n);
			for (size_t i = 0; i < n; i++)
			{
				push_back(val);
			}
		}
		vector<T>& operator=(vector<T> v)
		{
			swap(v);
			return *this;
		}
		size_t size() const
		{
			return _finish - _start;
		}
		size_t capacity() const 
		{
			return _endofstorage - _start;
		}
		void resize(size_t n,const T& val=T())
		{
			if (n < capacity())
			{
				_finish = _start + n;
			}
			else
			{
				reserve(n);
				while (_finish < _start + n)
				{
					*_finish = val;
					_finish++;
				}
			}
		}
		void reserve(size_t n)
		{
			if (n> capacity())
			{
				size_t old = size();
				T* tmp = new T[n];
				//memcpy(tmp, _start, size() * sizeof(T));  //T 为string时不能深拷贝
				for (size_t i = 0; i < old; i++)
				{
					tmp[i] = _start[i];
				}
				delete[] _start;
				_start = tmp;
				_finish = _start + old;
				_endofstorage = _start + n ;
			}
			else
			{
				_finish = _start + n;
			}
		}
		void push_back(const T& val)
		{
			//判断容量
			if (_finish == _endofstorage)
			{
				reserve(capacity() == 0 ? 4 : capacity() * 2);
			}
			
			
			*_finish = val;
			++_finish;

		}
		void pop_back()
		{
			erase(end()-1);
		}
		iterator insert(iterator pos, const T& val)
		{
			assert(pos >= _start);
			assert(pos <= _finish);
			if (_finish == _endofstorage)
			{
				//记录pos位置
				size_t len = pos - _start;
				reserve(capacity() == 0 ? 4 : capacity() * 2);
				//更新pos   如果不更新  迭代器会失效
				pos = _start + len;
				
			}
			iterator it = _finish-1;
			
			while (it >= pos)
			{
				*(it + 1) = *it;
				--it;
			}
			*pos = val;
			_finish++;
			return pos;
		}
		iterator erase(iterator pos)
		{
			assert(pos >= _start);
			assert(pos <= _finish);
			if (empty())
				return pos;
			iterator it = pos;
			while (it <= _finish)
			{
				*it = *(it + 1);
				it++;
			}
			_finish--;
			return pos;
		}
		iterator erase(iterator first, iterator last)
		{
			assert(first >= _start);
			assert(first <= _finish);
			size_t len = last - first;_finish-=(len);
			if (empty())
				return first;
			if (last >= _finish)
			{
				_finish = first;
			}
			else
			{
				iterator it = first;
				int i = 0;
				while (it <= last)
				{
					*it = *(last+i);
					i++;
					it++;
				}
				while (it <= _finish)
				{
					*it = *(it + len);
					it++;
				}
				
			}
			return first;
		}
		bool empty()
		{
			return _start == _finish;
		}
		T& operator[] (size_t pos)
		{
			assert(pos < size());
			return _start[pos];
		}
		const T& operator[] (size_t pos) const
		{
			assert(pos < size());
			return _start[pos];
		}
		iterator begin()
		{
			return _start;
		}
		iterator end()
		{
			return _finish;
		}
		const_iterator begin() const
		{
			return _start;
		}
		const_iterator end() const
		{
			return _finish;
		}
		T& front()
		{
			return *begin();
		}
		const T& front() const
		{
			return *begin();
		}
		T& back()
		{
			return *(end() - 1);
		}
		const T& back() const
		{
			return *(end() - 1);
		}
		void clear()
		{
			_finish = _start;
		}
		void swap(vector<T>& x)
		{
			std::swap(_start, x._start);
			std::swap(_finish, x._finish);
			std::swap(_endofstorage, x._endofstorage);
		}
	private:
		iterator _start=nullptr;
		iterator _finish=nullptr;
		iterator _endofstorage=nullptr;
	};




	template<typename T>
	void print_vector(const vector<T>& v)
	{
		cout << "[]" << endl;
		for (int i = 0; i < v.size(); i++)
		{
			cout << v[i] << ' ';
		}
		cout << endl;




		typename vector<T>::iterator it = v.begin();
		//auto it = v.begin();

		cout << "iterator" << endl;
		while (it != v.end())
		{
			cout << *it << ' ';
			it++;
		}
		cout << endl;


		cout << "autofor" << endl;
		for (auto e : v)
		{
			cout << e << ' ';
		}
		cout << endl;
	}
}