#pragma once
namespace yqx
{
template
class vector
{
public:
typedef T* iterator;
typedef const T* const_iterator;
vector()//构造
:_start(nullptr)
,_finish(nullptr)
,_endofstorage(nullptr)
{}
//模板里边套模板
//拷贝构造函数，迭代器用作参数，来构造一个对象
template
vector(InputIterator first, InputIterator last)
: _start(nullptr)
, _finish(nullptr)
, _endofstorage(nullptr)
{
while (first != last)
{
push_back(*first);
++first;
}
}
//传统写法
//现代写法
vector(const vector& v)
:_start(nullptr)
, _finish(nullptr)
, _endofstorage(nullptr)
{
vector tmp(v.begin(), v.end());
swap(tmp);
}
vector& operator=( vector v)
{
swap(v);
return *this;
}
~vector()
{
delete[] _start;
_start = _finish = _endofstorage = nullptr;
}
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 sz = size();
T* tmp = new T[n];
if (_start)
{
//memcpy(tmp, _start, sizeof(T) * sz);按字节拷贝，浅拷贝，若数组内容是字符串，就会出错。因此要用深拷贝
for (size_t i = 0; i < sz; ++i)
{
tmp[i] = _start[i];//调用的是T的operator= 深拷贝
}
delete[] _start;
}
_start = tmp;
_finish = tmp + sz;
_endofstorage = tmp + n;
}
}
//resize的特点：
//（1）n<=size()》》size()变成n，但是capacity不变
//（2）size()capacity()》》先扩容，从从size（）到n之间的元素初始化成val，size()变成n
void resize(size_t n, const T& val = T())//给T类型的缺省值例如int i = int();
{
size_t num = size();
if (n > size())
{
if (n > capacity())
{
reserve(n);
}
iterator it = _finish;
while (it < _start + n)
{
*it = val;
++it;
}
}
_finish = _start + n;
}
void pop_back()
{
erase(_finish - 1);
}
void push_back(const T& x)
{
insert(_finish, x);
}
T& operator[](size_t i)
{
assert(i < size());
return *(_start + i);
}
const T& operator[](size_t i)const
{
assert(i < size());
return *(_start + i);
}
void insert(iterator pos, const T& x)
{
assert(pos >= _start && pos <= _finish);
if (_finish == _endofstorage)
{
int n = pos - _start;
size_t newcapacity = capacity() == 0?2 :(2 * capacity());
reserve(newcapacity);
pos = _start + n;//迭代器重定向
}
iterator end = _finish - 1;
while (end >= pos)
{
*(end + 1) = *(end);
--end;
}
* pos = x;
++_finish;
}
iterator erase(iterator pos)
{
assert(pos >=_start && pos < _finish);
iterator it = pos;
//iterator vit = pos+1;
int n = pos - _start;
while (it < _finish)
{
*it = *(it + 1);
++it;
}
--_finish;
//pos = vit;
pos = _strat+n;
return pos ;
}
size_t size()
{
return _finish - _start;
}
size_t capacity()
{
return _endofstorage - _start;
}
size_t size()const
{
return _finish - _start;
}
size_t capacity()const
{
return _endofstorage - _start;
}
void swap(vector& v)
{
::swap(_start, v._start);// :: 的作用使用类外的作用域
::swap(_finish, v._finish);
::swap(_endofstorage, v._endofstorage);
}
private:
iterator _start;
iterator _finish;//_start+_size
iterator _endofstorage;//_start+_capacity
};
//以下为测试用例
void test_vector1()
{
vectorv;
v.push_back(1);
v.push_back(2);
v.push_back(3);
v.push_back(4);
vector::iterator vit = v.begin();
while (vit != v.end())
{
cout << *vit << " ";
++vit;
}
cout << endl;
for (auto e : v)
{
cout << e << " ";
}
cout << endl;
for (auto& e : v)
{
e *= 2;
}
for (auto e : v)
{
cout << e << " ";
}
cout << endl;
for (size_t i = 0; i < v.size(); ++i)
{
cout << v[i] << " ";
}
cout << endl;
}
void test_vector2()
{
vectorv;
v.push_back(1);
v.push_back(2);
v.push_back(3);
v.push_back(4);
v.insert(v.begin(), 6);
v.insert(v.begin()+2, 1232);
for (auto e : v)
{
cout << e << " ";
}
cout << endl;
}
void test_vector3()
{
vectorv;
v.push_back(1);
v.push_back(2);
v.push_back(3);
v.push_back(4);
v.push_back(6);
v.push_back(4);
vector::iterator vit = v.begin();
while (vit != v.end())
{
if (*vit % 2 == 0)
{
vit = v.erase(vit);
}
else
{
++vit;
}
}
for (auto e : v)
{
cout << e << " ";
}
cout << endl;
}
void test_vector4()
{
vectorv;
v.reserve(10);
v.push_back(1);
v.push_back(2);
v.push_back(3);
v.push_back(4);
v.push_back(5);
v.push_back(6);
v.push_back(7);
vector::iterator vit = v.begin();
for (auto e : v)
{
cout << e << " ";
}
cout << endl;
v.resize(4);
for (auto e : v)
{
cout << e << " ";
}
cout << endl;
v.resize(8,8);
for (auto e : v)
{
cout << e << " ";
}
cout << endl;
v.resize(13,1);
for (auto e : v)
{
cout << e << " ";
}
cout << endl;
}
void test_vector5()
{
vector v;
v.push_back(1);
v.push_back(2);
v.push_back(3);
v.push_back(4);
vector v2(v);
for (size_t i = 0; i < v.size(); ++i)
{
cout << v[i] << " ";
}
cout << endl;
for (size_t i = 0; i < v2.size(); ++i)
{
cout << v2[i] << " ";
}
cout << endl;
vector v3=v;
for (size_t i = 0; i < v3.size(); ++i)
{
cout << v3[i] << " ";
}
cout << endl;
}
void test_vector6()
{
vector v;
v.push_back("111");
v.push_back("222");
v.push_back("333");
v.push_back("444");
vector::iterator vit = v.begin();
v.erase(vit);
vit++;
for(auto e : v)
{
cout << e << " ";
}
cout << endl;
}
}
迭代器失效问题：
迭代器失效的原因： （1）迭代器的意义与之前的意义发生改变 （2）迭代器（原生指针）变成野指针 1. push_back insert resize reserve等可能会扩容的接口都会导致vector迭代器失效，但是 list迭代器不会失效，因为在list容器中，每个节点都是相互独立的，插入一个新节点不会影响 pos的指向位置 2.删除list,vector迭代器都会失效 list中erase使迭代器失效的原因：节点被删除，则会发生free（node）,此时迭代器会变成野指针。 vector中erase是迭代器失效的原因：迭代器是的意义与删除之前迭代器的意义不同（指向改变） vectorv; v.push_bask(1); v.push_bask(2); v.push_bask(3); v.push_bask(4); vector ::iterator it = v.begin(); while(it != v.end()) { if(*it % 2 ==0) { it = v.erase(it); } ++it; }
operator[]与at的区别：
at会做边界检查，而operator[]不会做边界检查
vector中的迭代器是原生指针，因此可以直接对vector的迭代器进行 * += +等操作；
