手写 C++ Vector 容器底层原理与实现

手写 C++ Vector 容器底层原理与实现

Vector 作为 C++ STL 中最常用的序列容器，其核心在于对动态内存的高效管理。在实现层面，我们主要依赖三个关键指针来追踪数据状态：指向起始位置的 _start，指向有效数据末尾的 _finish，以及指向已分配存储空间末尾的 _endofstorage。

核心成员变量与初始化

这三个指针构成了 Vector 的骨架。构造函数负责将它们初始化为空状态，确保对象创建时处于安全可用状态。

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

namespace Solution
{
	template<class T>
	class vector
	{
	public:
		typedef T* iterator;
		typedef const T* const_iterator;
		vector()
			:_start(nullptr)
			,_finish(nullptr)
			,_endofstorage(nullptr)
		{}
		//实现拷贝构造，先开一样的空间，再拷贝
		vector(const vector<T>& v)
			:_start(nullptr)
			,_finish(nullptr)
			,_endofstorage(nullptr)
		{
			reserve(v.capacity());
			//因为 memcpy 是浅拷贝，故不考虑，用深拷贝赋值拷贝
			if (_start)
			{
				for (size_t i = 0; i < v.size(); ++i)
				{
					*(_start + i) = *(v._start + i);
				}
			}
			_finish = _start + v.size();
			_endofstorage = _start + v.capacity();
		}
		~()
		{
			[] _start;
			_start = _finish = _endofstorage = ;
		}
		
		{
			 (_finish == _endofstorage)
			{
				 capacity1 = ();
				 newcapacity = capacity1 ==  ?  :  * capacity1;
				(newcapacity);
			}
			*_finish = val;
			++_finish;
			
		}

		
		{
			(_start != _finish);
			_finish--;
		}
		
		{
			(pos >= _start && pos <= _finish);
			 (_finish == _endofstorage)
			{
				 capacity1 = ();
				 newcapacity = capacity1 ==  ?  :  * capacity1;
				(newcapacity);
			}

			iterator end1 = () - ;
			 (end1 >= pos)
			{
				*(end1) = *end1;
				--end1;
			}
			*pos = val;
			_finish++;
		}

		{
			(pos >= _start && pos < _finish);
			 (pos < _finish)
			{
				*pos = *(pos + );
				++pos;
			}
			--_finish;
		}

		{
			 (n < ())
			{
				_finish = _start + n;
			}
			
			{
				(n);
				 (_finish < _start + n)
				{
					*_finish = val;
					++_finish;
				}
			}
		}

		{
			 (n > ())
			{
				 sz = ();
				T* tmp =  T[n];

				
				 ( i = ; i < sz; ++i)
				{
					*(tmp + i) = *(_start + i);
				}

				[] _start;
				_start = tmp;
				_finish = tmp + sz;
				_endofstorage = tmp + n;
			}
		}

		
		{
			 _start;
		}
		
		{
			 _finish;
		}
		

		T& []( n)
		{
			(n < ());
			 *(_start + n);
		}
		
		vector<T>& =( vector<T>& v)  
		{
			 ( != &v)
			{
				vector<T> (v);
				(v1);
			}
			 *;
		}
		
		{
			(_start, v._start);
			(_finish, v._finish);
			(_endofstorage, v._endofstorage);
		}


		{
			 _finish - _start;
		}
		{
			 _endofstorage - _start;
		}
	:
		T* _start;
		T* _finish;
		T* _endofstorage;
	};
}