知识点：
① 因为vector是模版，所以声明和定义都放在.h中，防止出现编译错误
.h不会被编译，在预处理中.h在.cpp中展开所以在编译时只有.cpp
而 .cpp顺序编译，只会进行向上查找，因此至少有函数的声明。
②memcpy的复习
memcpy(dest , source,大小)
③ 拷贝构造也是构造函数（拷贝构造函数我们必须写，我们写的是深拷贝）
但是有了拷贝构造函数，编译器就不会自己生成构造函数了，
因为拷贝构造也是构造函数的一种，所以要强制生成
强制编译器生成默认的构造函数,使用参数的缺省值生成默认构造函数
vector() = default;④拷贝构造函数和赋值重载函数的现代写法
⑤扩容之后，迭代器失效问题
目录
vector.h
test.cpp
vector.h
#pragma once
#include<iostream>
#include<assert.h>
#include<algorithm>namespace bit
{template<class T>class vector{public://迭代器的实现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;}size_t size()const{return _finish - _start;}size_t capacity() const{return _end_of_storage - _start;}//用迭代器区间构造函数//vector<int> v2(v1.begin() + 1, v1.end());//函数模板，写的不是iterator ，目的支持任意容器的迭代器 eg: list<int>的迭代器template<class InputIterator>vector(InputIterator first, InputIterator last){while (first != last){push_back(*first);++first;}}//构造函数,没必要自己写//vector()//:_start(nullptr)//,_finish(nullptr)//,_end_of_storage(nullptr)//{}// 拷贝构造也是构造函数（拷贝构造函数我们必须写，我们写的是深拷贝）// 但是有了拷贝构造函数，编译器就不会自己生成构造函数了，//因为拷贝构造也是构造函数的一种，所以要强制生成// 强制编译器生成默认的构造函数,使用参数的缺省值构造vector() = default;//n个value的构造函数//vector(10,10)// C++对内置类型也补充了内置类型的构造函数,看下面的test5中j=0// std::string s1("c");//vector(20,s1)vector(size_t n, const T& value = T())//T()代表用默认构造函数生成的匿名对象{reserve(n);//提高效率for (size_t i = 0; i < n; i++){push_back(value);}}//vector<int>v4(10, 1);//解决编译器的选择问题vector(int n, const T& value = T()){reserve(n);//提高效率for (int i = 0; i < n; i++){push_back(value);}}//拷贝构造函数//vector<int> v3(v2);vector(const vector<T>& v2){reserve(v2.capacity());for (auto e: v2){push_back(e);}}//赋值重载函数（利用形参时的拷贝构造生成的临时对象）//v3= v2;vector<T>& operator=( vector<T> v)//v是v2的临时拷贝，只需要将v3变成v即可（现代写法）{swap(v);return *this;}//析构函数~vector(){if (_start){delete[]_start;_start = _finish = _end_of_storage = nullptr;}}void reserve(size_t n){if (n > capacity()){size_t old_size = size();T* tmp = new T[n];if (_start)//不为空，拷贝原数据{memcpy(tmp, _start, sizeof(T) * size());delete[] _start;}_start = tmp;_finish = tmp + old_size;//更新_finish_end_of_storage = tmp + n;}}void resize(size_t n, const T& value = T()){if (n <= size()){_finish = _start + n;}else{if (capacity() < n){reserve(n);}while (size() < n){push_back(value);}}}T& operator[](size_t i){assert(i < size());assert(i >= 0);return _start[i];}const T& operator[](size_t i) const{assert(i < size());assert(i >= 0);return _start[i];}void push_back(const T& x){if (capacity() == size()){size_t newcapacity = capacity() == 0 ? 4 : capacity() * 2;reserve(newcapacity);}_start[size()] = x;//*_finish =x;_finish++;}void pop_back(){assert(size() > 0);--_finish;}void swap(vector<T>& v){std::swap(_start, v._start);std::swap(_finish, v._finish);std::swap(_end_of_storage, v._end_of_storage);}//在pos位置之前插入Xiterator insert(iterator pos, const T& x){assert(pos >= _start);//不要忘了断言assert(pos <= _finish);if (_finish == _end_of_storage)//扩容会导致迭代器失效，要去更新pos{size_t length = pos - _start;size_t newcapacity = capacity() == 0 ? 4 : capacity() * 2;reserve(newcapacity);pos = _start + length;}iterator it1 = _finish;while (it1 != pos)//挪动数据{*(it1) = *(it1 - 1);--it1;}*pos = x;_finish++;return pos;}iterator erase(iterator pos)//返回擦出后的下一个{assert(pos >= _start);assert(pos < _finish);size_t len = pos - _start;iterator it2 = pos;while (it2 < _finish){*(it2) = *(it2 + 1);++it2;}--_finish;if (size() > 0){return _start + len;}else{return nullptr;}}private:iterator _start = nullptr;//头iterator _finish = nullptr;//存储内容的尾iterator _end_of_storage = nullptr;//存储空间的尾部};void test1(){vector<int> v1;v1.push_back(1);v1.push_back(2);v1.push_back(3);v1.push_back(4);v1.push_back(5);v1.push_back(6);v1.push_back(7);v1.push_back(8);v1.push_back(9);for (auto e: v1){std::cout << e << " ";}std::cout << std::endl;std::cout << v1.size() << " " << v1.capacity()<< std::endl;v1.resize(12,666);for (auto e : v1){std::cout << e << " ";}std::cout << std::endl;std::cout << v1.size() << " " << v1.capacity() << std::endl;v1.resize(6);for (auto e : v1){std::cout << e << " ";}std::cout << std::endl;std::cout << v1.size() << " " << v1.capacity() << std::endl;v1.pop_back();v1.pop_back();v1.pop_back();v1.pop_back();v1.pop_back();v1.pop_back();for (auto e : v1){std::cout << e << " ";}std::cout << std::endl;std::cout << v1.size() << " " << v1.capacity() << std::endl;/*v1.pop_back();*/for (auto e : v1){std::cout << e << " ";}std::cout << std::endl;std::cout << v1.size() << " " << v1.capacity() << std::endl;}void test2(){vector<int> v1;for (auto e : v1){std::cout << e << " ";}std::cout << std::endl;std::cout << v1.size() << " " << v1.capacity() << std::endl;v1.insert(v1.begin(), 10);v1.insert(v1.end(), 20);v1.insert(v1.end(), 30);v1.insert(v1.end(), 40);v1.insert(v1.end(), 50);v1.insert(v1.end(), 60);for (auto e : v1){std::cout << e << " ";}std::cout << std::endl;std::cout << v1.size() << " " << v1.capacity() << std::endl;v1.erase(v1.end()-1);v1.erase(v1.end()-1);int* it = v1.erase(v1.begin());std::cout << *it;/* for (auto e : v1){std::cout << e << " ";}std::cout << std::endl;std::cout << v1.size() << " " << v1.capacity() << std::endl;*/}void test3(){vector<int> v1;v1.push_back(10);v1.push_back(20);v1.push_back(30);v1.push_back(40);for (auto e : v1){std::cout << e << " ";}std::cout << std::endl;vector<int> v2;v2 = v1;for (auto e : v2){std::cout << e << " ";}std::cout << std::endl;}void test4(){vector<int> v1;v1.push_back(10);v1.push_back(20);v1.push_back(30);v1.push_back(40);for (auto e : v1){std::cout << e << " ";}std::cout << std::endl;vector<int> v2(v1.begin() + 1, v1.end());for (auto e : v2){std::cout << e << " ";}std::cout << std::endl;}void test5(){int x = 0;int k = int();int j(10);std::cout << x << " " << j << " " << k << std::endl;}void test6(){std::string s1("c");vector<std::string> v1(5);//第二个参数省略，用缺省值vector<std::string>v2(5, s1);vector<std::string>v3(5, "aa");//vector<std::string>v3(5, 1);会报错，系统认为与template<class InputIterator>更匹配//vector(InputIterator first,InputIterator last)vector<int> v4((size_t)5, 1);//5u指的是unsigned_intfor (auto e : v1){std::cout << e << " ";}std::cout << std::endl;for (auto e : v2){std::cout << e << " ";}std::cout << std::endl;for (auto e : v3){std::cout << e << " ";}std::cout << std::endl;for (auto e : v4){std::cout << e << " ";}std::cout << std::endl;vector<int> v5(10, 1);for (auto e : v5){std::cout << e << " ";}std::cout << std::endl;}}
test.cpp
#include"vector.h"int main()
{bit::test6();return 0;
}
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