【C++】vector模拟实现

实现以下功能：

构造函数：a.无参默认构造 b.n个val构造 c.迭代器区间构造 d.initializer_list构造，类似于数组 e.拷贝构造
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实现reserve接口
实现size()，capacity()接口
实现push_bakc接口，尾插
实现insert接口，位置插入
实现erase接口，位置删除
实现pop_back接口，尾删
实现empty接口，判断容器是否为空

实现迭代器

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

/*
inrsert
push_back

pop_back
erase

reserve
capacity()
size()
empty()

begin()
end()

operator[]
*/

namespace liu
{
template<class T>
class vector
{
public:
typedef T* iterator;
typedef const T* const_iterator;

复制代码

		vector()
			:_start(nullptr)
			,_finish(nullptr)
			,_endofstorage(nullptr)
		{}


		~vector()
		{
			if (_start)
			{
				delete[] _start;
			}
			_start = nullptr;
			_finish = nullptr;
			_endofstorage = nullptr;
		}

		template<class InputIterator>
		vector(InputIterator first, InputIterator last)//迭代器区间初始化
		{
			while (first!=last)
			{
				push_back(*first);
				++first;
			}
		}

		vector(size_t n, const T& val = T())//n个VAL初始化
		{
			reserve(n);//提前开好空间，减少消耗
			for (size_t i=0;i<n;i++)
			{
				push_back(val);
			}
		}

		vector(int n, const T& val = T())
		{
			reserve(n);//提前开好空间，减少消耗
			for (int i = 0; i < n; i++)
			{
				push_back(val);
			}
		}
		//v2(v1)
		vector(const vector<T>& v)//拷贝构造
			:_start(nullptr)
			, _finish(nullptr)
			, _endofstorage(nullptr)
		{
			reserve(v.capacity());
			for (auto& e:v)
			{
				push_back(e);
			}
		}

		vector(initializer_list<T> il)
		{
			reserve(il.size());
			{
				for (auto& e:il)
				{
					push_back(e);
				}
			}
		}

		void swap(vector<T>& v)
		{
			std::swap(_start,v._start);
			std::swap(_finish,v._finish);
			std::swap(_endofstorage,v._endofstorage);
		}

		vector<T>& operator=(vector<T> v)
		{
			swap(v);
			return *this;
		}



		iterator begin()
		{
			return _start;
		}

		iterator end()
		{
			return _finish;
		}

		const_iterator begin()const
		{
			return _start;
		}

		const_iterator end()const
		{
			return _finish;
		}

		T& operator[](size_t i)
		{
			assert(i<size());
			return _start[i];
		}

		const T& operator[](size_t i)const
		{
			assert(i < size());
			return _start[i];
		}


		void reserve(size_t n)//不仅是内部用，还要提供给外部用
		{
			if (n>capacity())
			{
				size_t oldSize = size();

				T* tmp = new T[n];
				if (_start)
				{
					for (size_t i=0;i<oldSize;i++)
					{
						tmp[i] = _start[i];
					}

					delete[] _start;
				}
				_start = tmp;
				_finish = _start + oldSize;
				_endofstorage = _start + n;
			}
			
		}

		size_t size()
		{
			return _finish - _start;
		}

		size_t capacity()
		{
			return _endofstorage - _start;
		}

		void push_back(const T& x)
		{
			if (_finish==_endofstorage)
			{
				reserve(capacity()==0?4:2*capacity());
			}

			*_finish = x;
			_finish++;
		}

		iterator insert(iterator pos,const T& val)
		{
			assert(pos>=_start&&pos<=_finish);
			if (_finish==_endofstorage)
			{
				size_t len = pos - _start;
				reserve(capacity() == 0 ? 4 : 2 * capacity());
				pos = _start + len;
			}
			iterator i = _finish-1;
			while(i>=pos)
			{
				*(i + 1) = *i;
				i--;
			}
			*pos = val;
			++_finish;
			return pos;//更新迭代器
		}

		iterator erase(iterator pos)
		{
			assert(pos >= _start && pos < _finish);
			iterator i = pos+1;
			while (i<_finish)
			{
				*(i-1) = *i;
				i++;
			}
			--_finish;
			return pos;
		}


		void pop_back()
		{
			assert(!empty());
			_finish--;
		}


		bool empty()
		{
			return _start == _endofstorage;
		}

	private:
		iterator _start;
		iterator _finish;
		iterator _endofstorage;
	};

}