《C++ vector 完全指南：vector的模拟实现》
文章目录
- 《C++ vector 完全指南：vector的模拟实现》
- 一、定义vector的成员变量
- 二、用vector实现动态二维数组
- 三、vector的接口实现
- 1.vector的默认成员函数
- （1）构造函数实现
- （2）析构函数实现
- （3）拷贝构造函数
- （4）赋值运算符重载
- 2.vector的迭代器实现
- 3.vector的容量操作函数
- 4.vector的访问操作函数
- 5.vector的修改操作函数
- 整体源代码介绍
- vector.h
- Test.cpp
一、定义vector的成员变量
vector的成员变量是三个迭代器，也可以说是三个指针。
二、用vector实现动态二维数组
三、vector的接口实现
1.vector的默认成员函数
（1）构造函数实现
我们就依次实现下面四种构造方式
（2）析构函数实现
这里要注意对_start判空，因为空的时候就不用再析构！
（3）拷贝构造函数
这里也可以是构造函数，也是拷贝构造函数！
（4）赋值运算符重载
这里直接选择swap交换函数就OK
2.vector的迭代器实现
vector中迭代器iterator就是一个指针。所以我们直接使用typedef实现即可
begin（）和end（）本质上都是指针
3.vector的容量操作函数
size（）、capacity（）、clear（）、empty（）都很简单！一看就懂！
reverse（）和string实现差不多，只要新容量大于旧容量就发生扩容！
4.vector的访问操作函数
这里面主要就是 数组的下表访问[ ]
5.vector的修改操作函数
这里面有：push_back 、 pop_back 、 insert 、 earse
push_back要考虑扩容的问题，前两个比较简单
整体源代码介绍
vector.h
代码如下（示例）：
#pragma once
#include<assert.h>
#include<list>
#include<string>namespace bit
{template<class T>class vector{public:typedef T* iterator;typedef const T* const_iterator;vector(){}// C++11 前置生成默认构造vector() = default;vector(const vector<T>& v){reserve(v.size());for (auto& e : v){push_back(e);}}// 类模板的成员函数，还可以继续是函数模版template <class InputIterator>vector(InputIterator first, InputIterator last){while (first != last){push_back(*first);++first;}}vector(size_t n, const T& val = T()){reserve(n);for (size_t i = 0; i < n; i++){push_back(val);}}vector(int n, const T& val = T()){reserve(n);for (int i = 0; i < n; i++){push_back(val);}}void clear(){_finish = _start;}// v1 = v3//vector<T>& operator=(const vector<T>& v)//{// if (this != &v)// {// clear();// reserve(v.size());// for (auto& e : v)// {// push_back(e);// }// }// return *this;//}void swap(vector<T>& v){std::swap(_start, v._start);std::swap(_finish, v._finish);std::swap(_end_of_storage, v._end_of_storage);}// v1 = v3//vector& operator=(vector v)vector<T>& operator=(vector<T> v){swap(v);return *this;}~vector(){if (_start){delete[] _start;_start = _finish = _end_of_storage = 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 old_size = size();T* tmp = new T[n];//memcpy(tmp, _start, old_size * sizeof(T));for (size_t i = 0; i < old_size; i++){tmp[i] = _start[i];}delete[] _start;_start = tmp;_finish = tmp + old_size;_end_of_storage = tmp + n;}}void resize(size_t n, T val = T()){if (n < size()){_finish = _start + n;}else{reserve(n);while (_finish < _start + n){*_finish = val;++_finish;}}}size_t size() const{return _finish - _start;}size_t capacity() const{return _end_of_storage - _start;}bool empty() const{return _start == _finish;}void push_back(const T& x){// 扩容if (_finish == _end_of_storage){reserve(capacity() == 0 ? 4 : capacity() * 2);}*_finish = x;++_finish;}void pop_back(){assert(!empty());--_finish;}iterator insert(iterator pos, const T& x){assert(pos >= _start);assert(pos <= _finish);// 扩容if (_finish == _end_of_storage){size_t len = pos - _start;reserve(capacity() == 0 ? 4 : capacity() * 2);pos = _start + len;}iterator end = _finish - 1;while (end >= pos){*(end + 1) = *end;--end;}*pos = x;++_finish;return pos;}void erase(iterator pos){assert(pos >= _start);assert(pos < _finish);iterator it = pos + 1;while (it != end()){*(it - 1) = *it;++it;}--_finish;}T& operator[](size_t i){assert(i < size());return _start[i];}const T& operator[](size_t i) const{assert(i < size());return _start[i];}private:iterator _start = nullptr;iterator _finish = nullptr;iterator _end_of_storage = nullptr;};/*void print_vector(const vector<int>& v){vector<int>::const_iterator it = v.begin();while (it != v.end()){cout << *it << " ";++it;}cout << endl;for (auto e : v){cout << e << " ";}cout << endl;}*/template<class T>void print_vector(const vector<T>& v){// 规定，没有实例化的类模板里面取东西，编译器不能区分这里const_iterator// 是类型还是静态成员变量//typename vector<T>::const_iterator it = v.begin();auto it = v.begin();while (it != v.end()){cout << *it << " ";++it;}cout << endl;for (auto e : v){cout << e << " ";}cout << endl;}template<class Container>void print_container(const Container& v){/*auto it = v.begin();while (it != v.end()){cout << *it << " ";++it;}cout << endl;*/for (auto e : v){cout << e << " ";}cout << endl;}void test_vector1(){vector<int> v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);for (size_t i = 0; i < v.size(); i++){cout << v[i] << " ";}cout << endl;vector<int>::iterator it = v.begin();while (it != v.end()){cout << *it << " ";++it;}cout << endl;for (auto e : v){cout << e << " ";}cout << endl;print_vector(v);vector<double> vd;vd.push_back(1.1);vd.push_back(2.1);vd.push_back(3.1);vd.push_back(4.1);vd.push_back(5.1);print_vector(vd);}void test_vector2(){std::vector<int> v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);v.push_back(5);print_container(v);/*v.insert(v.begin() + 2, 30);print_vector(v);*/int x;cin >> x;auto p = find(v.begin(), v.end(), x);if (p != v.end()){// insert以后p就是失效，不要直接访问，要访问就要更新这个失效的迭代器的值/*v.insert(p, 20);(*p) *= 10;*/p = v.insert(p, 40);(*(p + 1)) *= 10;}print_container(v);}void test_vector3(){std::vector<int> v;v.push_back(1);v.push_back(2);v.push_back(3);v.push_back(4);print_container(v);// 删除所有的偶数auto it = v.begin();while (it != v.end()){if (*it % 2 == 0){it = v.erase(it);}else{++it;}}print_container(v);}void test_vector4(){int i = int();int j = int(1);int k(2);vector<int> v;v.resize(10, 1);v.reserve(20);print_container(v);cout << v.size() << endl;cout << v.capacity() << endl;v.resize(15, 2);print_container(v);v.resize(25, 3);print_container(v);v.resize(5);print_container(v);}void test_vector5(){vector<int> v1;v1.push_back(1);v1.push_back(2);v1.push_back(3);v1.push_back(4);print_container(v1);vector<int> v2 = v1;print_container(v2);vector<int> v3;v3.push_back(10);v3.push_back(20);v3.push_back(30);v1 = v3;print_container(v1);print_container(v3);}void test_vector6(){vector<int> v1;v1.push_back(1);v1.push_back(2);v1.push_back(3);v1.push_back(4);v1.push_back(4);v1.push_back(4);vector<int> v2(v1.begin(), v1.begin() + 3);print_container(v1);print_container(v2);list<int> lt;lt.push_back(10);lt.push_back(10);lt.push_back(10);lt.push_back(10);vector<int> v3(lt.begin(), lt.end());print_container(lt);print_container(v2);vector<string> v4(10, "1111111");print_container(v4);vector<int> v5(10);print_container(v5);vector<int> v6(10u, 1);print_container(v6);vector<int> v7(10, 1);print_container(v7);}void test_vector7(){vector<string> v;v.push_back("11111111111111111111");v.push_back("11111111111111111111");v.push_back("11111111111111111111");v.push_back("11111111111111111111");print_container(v);v.push_back("11111111111111111111");print_container(v);}
}Test.cpp
代码如下（示例）：
#include<iostream>
#include<vector>
using namespace std;#include"vector.h"void test_vector1()
{vector<int> v1;vector<int> v2(10, 1);vector<int> v3(++v2.begin(), --v2.end());for (size_t i = 0; i < v3.size(); i++){cout << v3[i] << " ";}cout << endl;vector<int>::iterator it = v3.begin();while (it != v3.end()){cout << *it << " ";++it;}cout << endl;for (auto e : v3){cout << e << " ";}cout << endl;
}void TestVectorExpand()
{size_t sz;vector<int> v;v.reserve(100);sz = v.capacity();cout << "capacity changed: " << sz << '\n';cout << "making v grow:\n";for (int i = 0; i < 100; ++i){v.push_back(i);if (sz != v.capacity()){sz = v.capacity();cout << "capacity changed: " << sz << '\n';}}
}void test_vector2()
{//TestVectorExpand();vector<int> v(10, 1);v.reserve(20);cout << v.size() << endl;cout << v.capacity() << endl;v.reserve(15);cout << v.size() << endl;cout << v.capacity() << endl;v.reserve(5);cout << v.size() << endl;cout << v.capacity() << endl;
}void test_vector3()
{//TestVectorExpand();vector<int> v(10, 1);v.reserve(20);cout << v.size() << endl;cout << v.capacity() << endl;v.resize(15, 2);cout << v.size() << endl;cout << v.capacity() << endl;v.resize(25, 3);cout << v.size() << endl;cout << v.capacity() << endl;v.resize(5);cout << v.size() << endl;cout << v.capacity() << endl;
}void test_vector4()
{vector<int> v(10, 1);v.push_back(2);v.insert(v.begin(), 0);for (auto e : v){cout << e << " ";}cout << endl;v.insert(v.begin() + 3, 10);for (auto e : v){cout << e << " ";}cout << endl;vector<int> v1(5, 0);for (size_t i = 0; i < 5; i++){cin >> v1[i];}for (auto e : v1){cout << e << ",";}cout << endl;vector<char> v2;string s2;// \0vector<int> v3;// send(s2.c_str())
}void test_vector5()
{vector<int> v(5, 1);vector<vector<int>> vv(10, v);vv[2][1] = 2;// vv.operator[](2).operator[](1) = 2;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;
}
int main()
{test_vector5();
}//template<class T>
//class vector
//{
// T& operator[](int i)
// {
// assert(i < _size);
//
// return _a[i];
// }
//private:
// T* _a;
// size_t _size;
// size_t _capacity;
//};// vector<int>
//class vector
//{
// int& operator[](int i)
// {
// assert(i < _size);
//
// return _a[i];
// }
//private:
// int* _a;
// size_t _size;
// size_t _capacity;
//};
//
//// vector<vector<int>>
//class vector
//{
// vector<int>& operator[](int i)
// {
// assert(i < _size);
//
// return _a[i];
// }
//private:
// vector<int>* _a;
// size_t _size;
// size_t _capacity;
//};//int main()
//{
// bit::test_vector7();
//
// return 0;
//}
//using namespace std;
//#include<vector>
//void Test1()
//{
// vector<int> v = { 1,2,3,4,5,6,7,8 };
// vector<int>::iterator it = v.begin();
// cout << "顺序遍历：";
// while (it != v.end())
// {
// cout << *it << " ";
// ++it;
// }
// cout << endl;
// cout << "逆序遍历：";
// vector<int>::reverse_iterator rit = v.rbegin();
// while (rit != v.rend())
// {
// cout << *rit << " ";
// ++rit;
// }
//}
//void Test2()
//{
// //1.默认构造函数初始化
// vector<int> v1;
// //2.n个val初始化
// vector<int> v2(3, 2);
// string s("abcd");
// //3.利用迭代器区间初始化
// vector<int> v3(s.begin(), s.end());
// //4.拷贝构造
// vector<int> v4(v3);
// //5.赋值重载
// v2 = v3;
// //6.可变参数列表初始化
// vector<int> v5 = { 1,2,3,4,5 };
// //vector<char> v6 = v4;//error 不同类型不能赋值
//}
//void Test3()
//{
// vector<int> v = { 1,2,3,4,5 };
// cout << v.size() << endl;
// cout << v.capacity() << endl;
//}
//void TestExpand()
//{
// size_t sz;
// vector<int> v;
// sz = v.capacity();
// cout << "making v grow:" << endl;
// for (int i = 0; i < 100; ++i)
// {
// v.push_back(i);
// if (sz != v.capacity())
// {
// sz = v.capacity();
// cout << "capacity changed: " << sz << endl;
// }
// }
//}
//void Test4()
//{
// vector<int> v1 = { 1,2,3,4,5 };
// cout << "v1的有效长度为：" << v1.size() << endl;
// cout << "v1的容量大小为：" << v1.capacity() << endl;
// v1.reserve(10);
// cout << "v1的有效长度为：" << v1.size() << endl;
// cout << "v1的容量大小为：" << v1.capacity() << endl;
// v1.resize(8, 10);
// for (auto& e : v1)
// {
// cout << e << " ";
// }
//}
//// error
////因为reserve只是改变了容量capacity并没有改变size，
////而operator[]访问时元素时是禁止访问下标size以后的元素的，一旦访问就会直接报错
//void Test5()
//{
// vector<int> v;
// v.reserve(10);
// for (int i = 0; i < 10; i++)
// {
// v[i] = i;
// }
// for (auto& e : v)
// {
// cout << e << " ";
// }
//}
//void Test6()
//{
// vector<int> v = { 1,2,3,4,5 };
// for (int i = 0; i < v.size(); i++)
// {
// cout << v[i] << " ";
// }
// cout << endl;
// cout << "front：" << v.front() << endl;
// cout << "back：" << v.back() << endl;
//}
//void Test7()
//{
// vector<int> v = { 1,2,3,4,5,6 };
// cout << "back：" << v.back() << endl;
// //尾插
// v.push_back(7);
// //尾删
// cout << "back：" << v.back() << endl;
// v.pop_back();
// cout << "back：" << v.back() << endl;
// vector<int> vv = { 6,5,4,3,2,1 };
// //n个val赋值给原数组
// vv.assign(3, 2);
// for (int i = 0; i < vv.size(); i++)
// {
// cout << vv[i] << " ";
// }
// cout << endl;
// vv.swap(v);
// for (int i = 0; i < v.size(); i++)
// {
// cout << v[i] << " ";
// }
// cout << endl;
// for (int i = 0; i < vv.size(); i++)
// {
// cout << vv[i] << " ";
// }
//}
//void Test8()
//{
// vector<int> myvector(3, 100);
// vector<int>::iterator it = myvector.begin();
// //1.向指定位置插入一个元素
// it = myvector.insert(it, 200);
// cout << "myvector contains:";
// for (it = myvector.begin(); it < myvector.end(); it++)
// cout << ' ' << *it;
// cout << endl;
// //2.向指定位置插入n个元素
// myvector.insert(it, 2, 300);
// cout << "myvector contains:";
// for (it = myvector.begin(); it < myvector.end(); it++)
// cout << ' ' << *it;
// cout << endl;
// //3.向指定位置插入一段迭代器区间
// it = myvector.begin();
// vector<int> anothervector(2, 400);
// cout << "myvector contains:";
// for (it = myvector.begin(); it < myvector.end(); it++)
// cout << ' ' << *it;
// cout << endl;
// it = myvector.begin();
// myvector.insert(it + 2, anothervector.begin(), anothervector.end());
// //4.向指定位置插入一段迭代器区间
// int myarray[] = { 501,502,503 };
// myvector.insert(myvector.begin(), myarray, myarray + 3);
// cout << "myvector contains:";
// for (it = myvector.begin(); it < myvector.end(); it++)
// cout << ' ' << *it;
// cout << endl;
//}
//void Test9()
//{
// //1.删除迭代器所指元素
// vector<int> myvector;
// for (int i = 1; i <= 10; i++)
// myvector.push_back(i);
// vector<int>::iterator it = myvector.erase(myvector.begin() + 5);
// it = myvector.erase(it);
// //2.删除一段迭代器区间
// it = myvector.erase(myvector.begin(), myvector.begin() + 3);
// cout << "myvector contains:";
// for (int i = 0; i < myvector.size(); ++i)
// cout << ' ' << myvector[i];
// cout << endl;
//}
////int main()
////{
//// //Test3();
//// //TestExpand();
//// //Test4();
//// //Test5();
//// //Test6();
//// //Test7();
//// //Test8();
//// Test9();
////}
//
//int main()
//{
// vector<int> v{ 1,2,3,4,5,6 };
// auto it = v.begin();
// v.assign(100, 8);
// while (it != v.end())
// {
// cout << *it << " ";
// ++it;
// }
// cout << endl;
// return 0;
//}
