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vscode 配置 lua

书坊尚 2023-11-17 阅读 39
学习c++stl

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目录

一、vector实际的底层原理

二、vector的模拟实现

         迭代器相关

         基本操作(迭代器失效问题)

        插入 

        删除 

        push_back()

        pop_back()

         swap()

         基本成员函数

         构造函数

        拷贝构造函数 

        析构函数 

        赋值运算符 

         空间管理

        基本状态 

         扩容操作

        resize() 

         重载[ ](最爱的运算符!!!)

 三、整体代码


一、vector实际的底层原理

class vector
{
public:
	typedef T* iterator;
	typedef const T* const_iterator;
private:
	iterator _start;  
	iterator _finish;
	iterator _endofstorage;
};

        配合图解明白: 

二、vector的模拟实现

         迭代器相关

        // Vector的迭代器是一个原生指针

        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;
        }

         基本操作(迭代器失效问题)

        插入 

 iterator insert(iterator pos, const T& x)//迭代器失效,返回新的迭代器解决
            {
                    assert(pos >= _start);
                    assert(pos <= finish);

                    if (_finish == _endOfStorage)
                    {
                        size_t len = pos - _start;//避免位置错误,因为在扩容后_start的地址会变化
                        reserve(capacity() == 0 ? 4 : capacity() * 2);
                        pos = start + len;//恢复位置
                    }

                    iterator end = _finish - 1;
                    while (end >= pos)//从后往前挪
                    {
                        *(end + 1) = *end;
                        --end;
                    }

                    *pos = x;
                    ++_finish;

                    return pos;
            }

        删除 

 

iterator erase(Iterator pos)//迭代器失效,返回新的迭代器解决
                {
                    assert(pos >= _start);
                    assert(pos < _finish);

                    iterator it = pos + 1;//定义一个变量用于删除
                    while (it < _finish)
                    {
                        *(it - 1) = *it;
                        ++it;
                    }

                    --_finish;

                    return pos;
            }

        push_back()

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

        *_finish = x;
        ++_finish;*/

                insert(end(), x);
            }

        pop_back()

            void pop_back()
            {
                assert(!empty());

                --_finish;
            }

         swap()

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

         基本成员函数

         构造函数

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

            vector()
            {}

            vector(int n, const T& value = T())
            {
                reserve(n);
                for (int i = 0; i < n; i++)
                {
                    push_back(value);
                }
            }

        template<class InputIterator>
        vector(InputIterator first, InputIterator last)
        {
            while (first != last)
            {
                push_back(*first);
                ++first;
            }
        }

        拷贝构造函数 


        vector(const vector<T>& v)
        {
            reserve(v.capacity());
            for (auto& e : v)
            {
                push_back(e);
            }
            }

        析构函数 

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

        赋值运算符 

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

         空间管理

        基本状态 

        size_t capacity() const
        {
            return _endofstorage - _start;
        }

        size_t size() const
        {
            return _finish - _start;
        }

        bool empty()const
        {
            return size() == 0;
        }

         扩容操作

        void reserve(size_t n)
        {
            if (n > capacity())
            {
                T* tmp = new T[n];
                size_t sz = size();

                if (_start)
                {
                    //memcpy(tmp, _start, sizeof(T) * sz)//这里用memcpy这里会导致string的vector出错,浅拷贝问题

                    for (size_t i = 0; i < sz; i++)
                    {
                        tmp[i] = _start[i];
                    }

                    delete[] _start;
                }
                _start = tmp;
                _finish = _start + sz;
                _endOfStorage = _start + n;
            }

        }

        resize() 

        void resize(size_t n, const T& value = T())
        {
            if (n < size())
            {
                _finish =_start + n;
            }
            else
            {
                reserve(n);
                while (_finish < _start + n)
                {
                    *_finish = val;
                    ++_finish;
                }
            }

        }

         重载[ ](最爱的运算符!!!)

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

        const T& operator[](size_t pos)const
        {
            assert(pos < size());

            return _start[pos];
            }

 三、整体代码

#pragma once
#define _CRT_SECURE_NO_WARNINGS 01
#include<iostream>
using namespace std;

namespace lt

{

    template<class T>

    class vector

    {

    public:

        // Vector的迭代器是一个原生指针

        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;
        }



            // construct and destroy

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

            vector(int n, const T& value = T())
            {
                reserve(n);
                for (int i = 0; i < n; i++)
                {
                    push_back(value);
                }
            }

        template<class InputIterator>
        vector(InputIterator first, InputIterator last)
        {
            while (first != last)
            {
                push_back(*first);
                ++first;
            }
        }

        vector(const vector<T>& v)
        {
            reserve(v.capacity());
            for (auto& e : v)
            {
                push_back(e);
            }
            }

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

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

            // capacity

             size_t capacity() const
        {
            return _endofstorage - _start;
        }

        size_t size() const
        {
            return _finish - _start;
        }

        bool empty()const
        {
            return size() == 0;
        }

        void reserve(size_t n)
        {
            if (n > capacity())
            {
                T* tmp = new T[n];
                size_t sz = size();

                if (_start)
                {
                    //memcpy(tmp, _start, sizeof(T) * sz)//这里用memcpy这里会导致string的vector出错,浅拷贝问题

                    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& value = T())
        {
            if (n < size())
            {
                _finish =_start + n;
            }
            else
            {
                reserve(n);
                while (_finish < _start + n)
                {
                    *_finish = val;
                    ++_finish;
                }
            }

        }



            ///access///

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

        const T& operator[](size_t pos)const
        {
            assert(pos < size());

            return _start[pos];
            }



            ///modify/

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

        *_finish = x;
        ++_finish;*/

                insert(end(), x);
            }

            void pop_back()
            {
                assert(!empty());

                --_finish;
            }

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

                iterator insert(iterator pos, const T& x)//迭代器失效,返回新的迭代器解决
            {
                    assert(pos >= _start);
                    assert(pos <= finish);

                    if (_finish == _endOfStorage)
                    {
                        size_t len = pos - _start;//避免位置错误,因为在扩容后_start的地址会变化
                        reserve(capacity() == 0 ? 4 : capacity() * 2);
                        pos = start + len;//恢复位置
                    }

                    iterator end = _finish - 1;
                    while (end >= pos)//从后往前挪
                    {
                        *(end + 1) = *end;
                        --end;
                    }

                    *pos = x;
                    ++_finish;
            }

                iterator erase(Iterator pos)//迭代器失效,返回新的迭代器解决
                {
                    assert(pos >= _start);
                    assert(pos < _finish);

                    iterator it = pos + 1;//定义一个变量用于删除
                    while (it < _finish)
                    {
                        *(it - 1) = *it;
                        ++it;
                    }

                    --_finish;

                    return pos;
            }

    private:

        iterator _start = nullptr; // 指向数据块的开始

        iterator _finish = nullptr; // 指向有效数据的尾

        iterator _endOfStorage = nullptr; // 指向存储容量的尾

    };

}

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