c++之 vector 容器

特点：是一种单端数组，可以动态扩展
动态扩展：不是在原有空间后边续接新的空间，而是寻找更大的内存，将原数据拷贝到新的空间，然后释放原空间

#include
#include
#include
using namespace std;
void myPrint(int val)
{
	cout << val << " ";
}
int main()
{
	//创建一个vector容器
	vectorv;
	//向容器中插入数据
	v.push_back(10);
	v.push_back(20);
	v.push_back(30);
	v.push_back(40);
	//通过迭代器访问容器中的数据
	
	for_each(v.begin(), v.end(), myPrint);
	cout << endl;
	system("pause");
	return 0;
}

#include
#include
#include
using namespace std;
class Person
{
public:
	Person(string name, int age)
	{
		this->name = name;
		this->age = age;
	}
	string name;
	int age;
};
void myPrint(Person p)
{
	cout << p.name << " " << p.age << endl;
}
int main()
{
	Person p1("a", 18);
	Person p2("b", 18);
	Person p3("c", 18);
	Person p4("d", 18);
	Person p5("e", 18);
	vectorv;
	v.push_back(p1);
	v.push_back(p2);
	v.push_back(p3);
	v.push_back(p4);
	v.push_back(p5);
	for_each(v.begin(), v.end(), myPrint);
	system("pause");
	return 0;
}

#include
using namespace std;
#include
#include
//void myPrint(vector>v)
//{
//	for (vector>::iterator it = v.begin(); it != v.end(); it++)
//	{
//		for (vector::iterator vit = (*it).begin(); vit != (*it).end(); vit++)
//		{
//			cout << *vit << " ";
//		}
//		cout << endl;
//	}
//}
void test()
{
	vector>v;
	vectorv1;
	vectorv2;
	vectorv3;
	vectorv4;
	for (int i = 0; i < 4; i++)
	{
		v1.push_back(i + 1);
		v2.push_back(i + 2);
		v3.push_back(i + 3);
		v4.push_back(i + 4);
	}
	v.push_back(v1);
	v.push_back(v2);
	v.push_back(v3);
	v.push_back(v4);
	for (vector>::iterator it = v.begin(); it != v.end(); it++)
	{
		for (vector::iterator vit = (*it).begin(); vit != (*it).end(); vit++)
		{
			cout << *vit << " ";
		}
		cout << endl;
	}


}
int main()
{
	test();
	
	system("pause");
	return 0;
}

• vector v;//默认构造函数
• vector(v.begin(),v.end());//将左闭右开区间内的元素拷贝给本身
• vector(n,elem);//构造函数将n个elem拷贝给自身
• vector(const vector &vec);//拷贝构造函数

#include
using namespace std;
#include
#include
void myPrint(vector& v)
{
	for (vector::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << endl;
	}
}
void test()
{
	vectorv1;
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}
	myPrint(v1);
	vectorv2(v1.begin(), v1.end());
	myPrint(v2);
	vectorv3(10, 100);
	myPrint(v3);
	vectorv4(v3);
	myPrint(v4);
}
int main()
{
	test();
	system("pause");
	return 0;
}

• vector& operator=（const vector &vec);//重载等号操作符
• assign(v.begin,v.end);//将左闭右开的数据赋值给本身
• assign(n,elem)//将n个elem拷贝给本身

#include
using namespace std;
#include
void myPrint(vector& v)
{
	for (vector::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}
void test()
{
	vectorv1;
	for (int i = 0; i < 10; i++)
	{
		v1.push_back(i);
	}
	vectorv2;
	v2 = v1;
	myPrint(v2);
	vectorv3;
	v3.assign(10, 100);
	myPrint(v3);
	vectorv4;
	v4.assign(v1.begin(),v1.end());
	myPrint(v4);
}
int main()
{
	test();
	system("pause");
	return 0;
}

• empty（）；//判断容器是否为空
• capacity（）；//判断容器的容量
• size（）；//返回容器中元素个数
• resize（int num)；//重新指定容器长度，若变长，默认值填充；变短，删除超出的元素。
• resize（int num，elem）；//重新指定容器长度，若变长，elem填充；变短，删除超出的元素。

#include
using namespace std;
#include
void myPrint(vector&v)
{
	for (vector::iterator it = v.begin(); it != v.end(); it++)
	{
		cout << *it << " ";
	}
	cout << endl;
}
void test()
{
	vectorv;
	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}
	myPrint(v);
	bool flag = v.empty();
	if (flag)
	{
		cout << "空！" << endl;
	}
	else
	{
		cout << "非空" << endl;
	}
	int capacity = v.capacity();
	cout << capacity << endl;
	cout << v.size() << endl;
	v.resize(15, 100);
	myPrint(v);
	v.resize(8);
	myPrint(v);
	
}
void test02()
{

}
int main()
{
	test();
	system("pause");
	return 0;
}

• push_back(elem);//尾部插入元素
• pop_back();//删除最后一个元素
• insert(const_iterator pos,ele)//迭代器指向位置pos插入元素ele
• insert(const_iterator pos,int count,ele)//迭代器指向位置pos插入count个元素ele
• erase(const_iterator pos)//删除迭代器指向的元素
• erase(const_iterator start,const_iterator end)//删除迭代器从start到end的元素
• clear();//删除容器中的所有元素

void test02()
{
	vectorv;
	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}
	v.pop_back();
	myPrint(v);
	v.insert(v.begin(),100);
	myPrint(v);
	v.insert(v.end(), 2, 100);
	myPrint(v);
	v.erase(v.begin());
	myPrint(v);
}

• at（int index);//返回index的值
• operato[];//返回index的值
• front();//返回第一个数据元素
• back();//返回最后一个数据元素

void test03()
{
	vectorv;
	for (int i = 0; i < 10; i++)
	{
		v.push_back(i);
	}
	cout << v.at(3) << endl;
	cout << v.at(0) << endl;//从0开始
	//cout << v.at(-1) << endl;//非法
	cout << v[4] << endl;//中括号直接访问
	cout << v.front() << endl;
	cout << v.back() << endl;;
}

• v.swap（v);//实现两个容器的交换

void test04()
{
	
	vectorv;
	for (int i = 0; i < 1000; i++)
	{
		v.push_back(i);
	}
	cout << v.capacity() << endl;
	cout << v.size() << endl;

	v.resize(3);
	cout << v.capacity() << endl;
	cout << v.size() << endl;
	vector(v).swap(v);//匿名对象调用swap方法，减少容量的浪费
	cout << v.capacity() << endl;
	cout << v.size() << endl;
}

• 预留的位置在初始化之后，才可以访问

void test05()
{
	int* p = NULL;
	int num = 0;
	vectorv;
	v.reserve(100000);
	for (int i = 0; i < 100000; i++)
	{
		v.push_back(i);
		if (p != &v[0])
		{
			p = &v[0];
			num++;
		}
	}
	cout << num << endl;
}