《C++ vector 完全指南：vector的模拟实现》

《C++ vector 完全指南：vector的模拟实现》

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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。

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二、用vector实现动态二维数组

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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

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（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！

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（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！

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（4）赋值运算符重载

这里直接选择swap交换函数就OK

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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

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3.vector的容量操作函数

size（）、capacity（）、clear（）、empty（）都很简单！一看就懂！

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reverse（）和string实现差不多，只要新容量大于旧容量就发生扩容！

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4.vector的访问操作函数

这里面主要就是 数组的下表访问[ ]

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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

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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;
//}

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