STL-vector模拟实现

#pragma once
#include<assert.h>
#include<iostream>
using std::cout;
using std::endl;
using std::cin;

namespace test
{

    //#include<algorithm>
    //模板参数省略:1.作为时  2.作为类型名
    template <class T> //数组名:类型名:xx数组
    class vector
    {
    public:
        //成员类型 //也可以用内部类,但C++都是typedef居多,不喜欢内部类
        typedef T* iterator;
        typedef const T* const_iterator;
    private:
        //构造函数太多,初始化列表重复太多麻烦,直接给缺省参数方便//C++11
        iterator _start = nullptr; //数组头
        iterator _finish = nullptr;//数组有效数据尾的下一个(类似\0位置)
        iterator _end_of_storage = nullptr;//数组容量尾的下一个位置,有效空间的下一个位置

    public:
        //无参构造
        vector()
        {}
        //有参构造:开辟n个空间,1.数量 2开辟对象空间
        vector(size_t n, const T& val = T()) //缺省值为显式匿名构造,基本类型也支持
        {
            //_start = new T[n];
            //_finish = _start + n;
            //_end_of_storage = _start + n;
            //for (size_t i = 0; i < n; ++i)
            //{
            //    _start[i] = val;
            //}
            reserve(n);
            for (size_t i = 0; i < n; ++i)
            {
                push_back(val);
            }
        }
        //有参构造整型重载
        vector(int n, const T& val = T())

        {
            reserve(n);
            for (size_t i = 0; i < n; ++i)
            {
                push_back(val);
            }
        }
        //迭代器构造
        template <class InputIterator>
        vector(InputIterator first, InputIterator last)

        {
            //size_t sz = last - first;
            //_start = _finish = new T[sz];
            //while (first != last)
            //{
            //    *_finish = *first;
            //    ++first;
            //    ++_finish;
            //}
            //_end_of_storage = _start + sz;
            while (first != last)
            {
                push_back(*first);
                ++first;
            }
        }

        //C++11 initializer_list 构造
        vector(std::initializer_list<T> il) //常量不能引用
        {
            //两种写法
            //typename std::initializer_list<T>::iterator it = il.begin();
            //while (it != il.end())
            //{
            //    push_back(*it);
            //    ++it;
            //}

            for (auto e : il)
            {
                push_back(e);
            }
        }

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

        //拷贝构造
        vector(const vector<T>& v)
        {
            //_start = new T[v.capacity()];
            //for (size_t i = 0; i < v.size(); ++i)
            //{
            //    _start[i] = v._start[i];//这里可能用到重载=,从而实现深拷贝
            //}
            //_finish = _start + v.size();
            //_end_of_storage = _start + v.capacity();
            vector<T> tmp(v.begin(), v.end());
            swap(tmp);

        }

        void swap(vector<T>& v)
        {
            //不能使用赋值,死循环
            //_start = v._start;
            //_finish = v._finish;
            //_end_of_storage = v._end_of_storage;

            //由于是拷贝的空间,且不能使用赋值,故交换掉,原先的会释放掉,
            //旧空间已经交换给v了,v会在出了作用域后回收,所以不用手动释放
            std::swap(_start, v._start);
            std::swap(_finish, v._finish);
            std::swap(_end_of_storage, v._end_of_storage);
        }

        vector<T>& operator=(vector<T> v) //深拷贝
            //赋值运算符重载：操作数是vector<vector<>>,在非初始化时走这里，初始化时时拷贝构造
            //传值传参，v是拷贝，所以是再次调了拷贝构造,新空间了,所以相当于深拷贝
        {
            swap(v);
            return *this;
        }

        iterator begin()
        {
            return _start;
        }

        iterator end()
        {
            return _finish;
        }
        const_iterator begin() const
        {
            return _start;
        }
        const_iterator end() const
        {
            return _finish;
        }

        //Capacity
        size_t capacity() const
        {
            return _end_of_storage - _start;
        }
        size_t size() const
        {
            return _finish - _start;
        }
        bool empty() const
        {
            return _start == _finish;
        }
        T& operator[](size_t pos) //_start的类型是对象,所以返回迭代器
        {
            assert(pos < size());
            return _start[pos];
        }
        const T& operator[](size_t pos)const
        {
            assert(pos < size());
            return _start[pos];
        }

        void resize(size_t n, const T& val = T())
        {
            if (n > capacity())
            {
                reserve(n);
            }

            if (n > size())
            {
                while (_finish < _start + n)
                {
                    *_finish = val;
                    ++_finish;
                }
            }
            else
            {
                _finish = _start + n;
            }
        }

        void reserve(size_t n) //扩容
        {
            if (n > capacity())
            {
                size_t sz = size();
                T* tmp = new T[n];
                //memcpy()//可能会有浅拷贝
                for (size_t i = 0; i < sz; ++i)
                {
                    tmp[i] = _start[i];
                }
                delete[] _start;
                _start = tmp;
                _finish = tmp + sz; //必须放在后面,因为size与_finish有关
                _end_of_storage = tmp + n;
            }
        }

        void push_back(const T& x)//尾插
        {
            if (_finish == _end_of_storage)
            {
                size_t newCapacity = capacity() == 0 ? 4 : capacity() * 2;
                reserve(newCapacity);
            }
            *_finish = x;
            ++_finish;
        }

        void pop_back() //尾删
        {
            //if (empty())
            //{
            //    return;
            //}
            assert(!empty());
            --_finish;
        }

        iterator insert(iterator pos, const T& val)//插入//返回原来插入的位置
        {
            assert(pos >= _start);
            assert(pos <= _finish);
            if (_finish == _end_of_storage)//reserve后迭代器失效
            {
                size_t len = _end_of_storage - _start;
                size_t newCapacity = capacity() == 0 ? 4 : capacity() * 2;
                reserve(newCapacity);

                pos = _start + len;                // 扩容会导致pos迭代器失效，需要更新处理一下
            }
            iterator end = _finish; //减少用end
            while (end >= pos)
            {
                *(end + 1) = *end;
                --end;
            }
            *pos = val;
            ++_finish;
            return pos; //防止迭代器可能因为扩容而失效,因此将迭代器作为返回值

        }
        iterator erase(iterator pos)//删除 //返回删除的下一个位置
        {
            assert(pos >= _start);
            assert(pos < _finish);
            iterator begin = pos + 1; //增加用begin
            while (begin != _finish)
            {
                *(begin - 1) = *begin;
                ++begin;
            }

            --_finish;
            return pos;
        }
    };

    //测试用例
    class Solution {
    public:
        vector<vector<int>> generate(int numRows) {
            vector<vector<int>> vv;
            vv.resize(numRows, vector<int>());

            for (size_t i = 0; i < vv.size(); ++i)
            {
                vv[i].resize(i + 1, 0);
                vv[i][0] = vv[i][vv[i].size() - 1] = 1;

                for (size_t j = 0; j < vv[i].size(); ++j)
                {
                    if (vv[i][j] == 0)
                    {
                        vv[i][j] = vv[i - 1][j - 1] + vv[i - 1][j];
                    }
                }
            }
            return vv;
        }
    };

    void test_vector4()
    {
        using namespace std;
        vector<vector<int>> vv = Solution().generate(3);
        for (size_t i = 0; i < vv.size(); ++i)
        {
            for (size_t j = 0; j < vv[i].size(); ++j)
            {
                cout << vv[i][j] << " ";
            }
            cout << endl;
        }
        cout << endl;

        vector<vector<int>> v3 = vv;//初始化=是拷贝构造 ,深拷贝过程中=是重载
        for (size_t i = 0; i < v3.size(); ++i)
        {
            for (size_t j = 0; j < v3[i].size(); ++j)
            {
                cout << v3[i][j] << " ";
            }
            cout << endl;
        }

        vector<int> v1;
        v1.resize(3, 1);
        vector<int> v2 = v1; //初始化=是拷贝构造
        for (auto e : v2)
        {
            cout << e << " ";
        }
    }

    void test_vector5()
    {
        vector<int> v = { 1,2,3,4,5 }; //initializer_list 初始化

    }

}