实现模板
#include<assert.h>#include<string.h>#include<iostream>#include<list>using namespace std;namespace fnc{template<class T>class vector{public:typedef T* iterator;typedef const T* const_iterator;//构造函数vector(){}//复制拷贝vector(const vector<T>& v){reserve(v.capacity());for (const auto& a : v){push_back(a);}}//迭代器区间构造template<class InputIterator>vector(InputIterator first, InputIterator last){while (first != last){push_back(*first);first++;}}vector(size_t n, const T& val = T()){resize(n, val);}vector(int n, const T& val = T()){resize(n, val);}void swap(vector<T>& v){std::swap(_start, v._start);std::swap(_finish, v._finish);std::swap(_endofstorage, v._endofstorage);}//赋值vector<T>& operator=(vector<T> v){swap(v);return *this;}//析构函数~vector(){if (_start){delete[] _start;_start = _finish = _endofstorage = nullptr;}}//返回对应的位置iterator begin(){return _start;}iterator end(){return _finish;}const_iterator begin() const{return _start;}const_iterator end() const{return _finish;}void reserve(size_t n){if (n > capacity()){size_t old = size();T* tmp = new T[n];if (_start){//memcpy(tmp, _start, sizeof(T) * old);//不建议for (int i = 0; i < old; i++){tmp[i] = _start[i];}delete[] _start;} _start = tmp;_finish = _start + old;_endofstorage = _start + n;}}void resize(size_t n, T val = T()){if (n > size()){if (n > capacity()){reserve(n);}//先记住之前的位置while (_finish < _start + n){*_finish = val;_finish++;}}else{_finish = _start + n;}}void push_back(const T& x){//满扩容if (_finish == _endofstorage){size_t newcapacity =capacity() == 0 ? 1 : capacity() * 2;reserve(newcapacity);}*_finish = x;_finish++;}void pop_back(){assert(size() > 0);--_finish;}iterator insert(iterator pos,const T& x){//确保pos是正确的范围内assert(pos >= _start && pos < _finish);if (_finish == _endofstorage){size_t distance = pos - _start;size_t newcapacity = capacity() == 0 ? 1 : capacity() * 2;reserve(newcapacity);pos = _start + distance;}//插入腾出空间//memmove(pos + 1, pos, sizeof(T) * (_finish - pos));//不建议iterator end = _finish - 1;while (end >= pos){*(end + 1) = *end;end--;}*pos = x;_finish++;return pos;}iterator erase(iterator pos){assert(pos >= _start && pos < _finish);//将对应位置挤掉//memmove(pos, pos + 1, sizeof(T) * (_finish - pos - 1));//不建议iterator it = pos + 1;while (it < _finish){*(it - 1) = *it;it++;}--_finish;return pos;}size_t capacity(){return _endofstorage - _start;}size_t size(){return _finish - _start;}size_t capacity() const{return _endofstorage - _start;}size_t size() const{return _finish - _start;}T& operator[](size_t pos){assert(pos < size());return _start[pos];}private:iterator _start=nullptr;iterator _finish=nullptr;iterator _endofstorage=nullptr;};首先我们看vector的成员函数，都是通过迭代器来确定具体位置的，
_start表示vector的起始位置，
_finish表示vector有效存储的结束位置，
_endodstorage表示当前开辟的空间指向最后的地址位置
下面通过实例来讲解一些需要注意的地方。
vector和const_vector
对于vector来说，实际上就是C语言的数组，这也就表明vector存储的元素的地址空间是连续的，所以这里的迭代器实际上表示的就是原始指针，但为了区别是否有const修饰，需要对他们进行简单的封装。
被const修饰的迭代器，只具有可读性，对于一些只读的函数，要多加const重载函数。
例子：
void print_vector(const vector<int>& v){for (auto a : v){cout << a << " ";}cout << endl;}void test_vector1(){vector<int> v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);vector<int>::iterator it = v.begin();while (it != v.end()){cout << *it << " ";it++;}cout << endl;for (auto a : v){cout << a << " ";}cout << endl;for (int i = 0; i < v.size(); i++){cout << v[i] << " ";}cout << endl;v.insert(v.begin(), 111);print_vector(v);v.insert(v.begin(), 110);print_vector(v);v.erase(v.begin() + 4);print_vector(v);v.erase(v.begin());print_vector(v);}如果这里没有添加const修饰的begin和end函数，那么将会报错，因为涉及到权限放大的问题。
resize()和reserve()
reserve()也就是对vector的容量进行扩容，
这里需要对原先的存储进行，方便后面进行对成员变量迭代器的定位。
这里要注意，_finish和_endofstorge都是相对于_start来取相对位置的，因为创建了一个新的空间。
resize()就是改变vector()的有效容量
T是泛型类型，T()表示取对应的默认构造参数，内置类型会取到0，或者nullptr；
自定义类型会根据构造参数进行初始化，取到对应的值；
void test_vector2(){vector<int> myvector;// set some initial content:for (int i = 1; i < 10; i++) myvector.push_back(i);myvector.resize(5);myvector.resize(8, 100);myvector.resize(12);cout << "myvector contains:";for (int i = 0; i < myvector.size(); i++)cout << ' ' << myvector[i];std::cout << endl;}
拷贝构造和赋值
这里会发现，我是在成员变量进行了声明，构造函数没有进行初始化；
一开始，我只是在构造函数进行了初始化，而在拷贝构造中没有进行初始化，那么由于这两个函数是构成重载的，所以像一些有指针的，由于没有进行初始化，会变成野指针，这样就会报错。
所以在这里总结：
void test_vector3(){vector<int> v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);vector<int> v1 = v;cout << "原来的v1 ";for (auto a : v1){cout << a << " ";}cout << endl;vector<int> v2;v2.push_back(22);v2.push_back(33);v2.push_back(44);v2.push_back(55);v1=v2;cout << "赋值后的v1 ";for (auto a : v1){cout << a << " ";}cout << endl;}
深浅拷贝的问题
先看例子
void test_vector4(){vector<string> v;v.reserve(10);v.push_back("xxx");v.push_back("xxx");v.push_back("xxx");v.push_back("xxx");v.push_back("xxx");v.push_back("xxx");for (auto a : v){cout << a << " ";}cout << endl;//n>sizev.resize(8);for (auto a : v){cout << a << " ";}cout << endl;//n>capacityv.resize(15, "yyyy");for (auto e : v){cout << e << " ";}cout << endl;//n<sizev.resize(3);for (auto e : v){cout << e << " ";}cout << endl;}
迭代器失效问题
void test_vector5(){vector<int> v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);v.push_back(6);//要求删除所有偶数vector<int>::iterator it = v.begin();while (it != v.end()){if (*it % 2 == 0){it=v.erase(it);}else{it++;}}for (auto e : v){cout << e << " ";}cout << endl;}
vector的其他构造
void test_vector6(){vector<int> v1;v1.push_back(1);v1.push_back(2);v1.push_back(3);v1.push_back(4);vector<int> v2(v1.begin(), v1.end());for (auto e : v2){cout << e << " ";}cout << endl;list<int> lt;lt.push_back(11);lt.push_back(22);lt.push_back(33);lt.push_back(44);vector<int> v3(lt.begin(), lt.end());for (auto e : v3){cout << e << " ";}cout << endl;int a[] = { 100,200,300 };vector<int> v4(a, a + 3);for (auto e : v4){cout << e << " ";}}
void test_vector7(){vector<string> v1(5, "1234");for (auto e : v1){cout << e << " ";}cout << endl;vector<int> v2(5, 1);for (auto e : v2){cout << e << " ";}cout << endl;}}
运行：
