功能:
vector与普通数组区别:
动态扩展:
容器: vector 算法: for each 迭代器: vector<int>::iterator
class person
{
public:
person(string name, int age)
{
this->m_name = name;
this->m_age = age;
}
string m_name;
int m_age;
};
vector<Person>v;
//向容器中添加数据
Person p1("aaa", 10);
Person p2("bbb", 20);
Person p3("ccc", 30);
v.push_back(p1);
v.push_back(p2);
v.push_back(p3);
类似于二维数组等
vector<vector<int>>v;
//创建小容器
vector<int>v1;
vector<int>v2;
vector<int>v3;
//添加数据
for (int i = 0; i < 4; i++)
{
v1.push_back(i + 1);
v2.push_back(i + 2);
v3.push_back(i + 3);
}
//将小容器插入到大容器
v.push_back(v1);
v.push_back(v2);
v.push_back(v3);
功能描述:
函数原型:
vector<int> v1;//默认构造,无参构造
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
Print(v1);
//通过区间的方式构造
vector<int>v2(v1.begin(), v1.end());
Print(v2);
//n个elem构造
vector<int>v3(10, 100);//10个100
Print(v3);
//拷贝构造
vector<int>v4(v1);
Print(v4);
功能描述:
函数原型:
vector<int>v1;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
Print(v1);
//赋值
vector<int>v2;
v2 = v1;
Print(v2);
//assign
vector<int>v3;
v3.assign(v1.begin(), v1.end());
Print(v3);
//n个elem
vector<int>v4;
v4.assign(10, 100);//10个100
Print(v4);
功能描述:
函数原型:
vector<int>v1;
cout << "赋值前v1的容量是:" << v1.capacity() << endl;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
Print(v1);
if (v1.empty())//为真,代表容器为空
{
cout << "为空" << endl;
}
else
{
cout << "不为空" << endl;
cout << "赋值后v1的容量是:" << v1.capacity()<< endl;//capacity>=size,size是容器内的元素个数
cout << "v1的大小是:" << v1.size()<<endl;
}
//重新指定大小
v1.resize(15);
Print(v1);//如果重新指定的大小比原来大,默认用0来填充新增的空间
v1.resize(16, 100);
Print(v1);//可以指定填充数
v1.resize(5);//如果重新指定的大小比原来小,则会删除多余的部分
Print(v1);
功能描述:
函数原型:
vector<int>v1;
//尾插
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
v1.push_back(100);
Print(v1);
//尾删
v1.pop_back();//删除100
Print(v1);
//插入
v1.insert(v1.begin(), 100);//参数1是迭代器,参数2是要插入的元素,插入在指定位置之前
Print(v1);
v1.insert(v1.begin(), 2, 1000);//插入2个1000
Print(v1);
//删除
v1.erase(v1.begin());//删除第一个1000 (参数也是迭代器)
Print(v1);
v1.erase(v1.begin(), v1.begin() + 3);
Print(v1);
//清空
v1.clear();
Print(v1);
功能描述:
函数原型:
vector<int>v1;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
//利用[]的方式来访问数组元素
for (int i = 0; i < v1.size(); i++)
{
cout << v1[i] << " ";
}
cout << endl;
//利用at访问
for (int i = 0; i < v1.size(); i++)
{
cout << v1.at(i) << " ";
}
cout << endl;
//获取第一个元素
cout << v1.front() << endl;
//获取最后一个元素
cout << v1.back() << endl;
功能描述:
函数原型:
//基本使用
vector<int>v1;
for (int i = 0; i < 10; i++)
{
v1.push_back(i);
}
cout << "交换前:" << endl;
Print(v1);
vector<int>v2;
for (int i = 10; i < 20; i++)
{
v2.push_back(i);
}
Print(v2);
cout << "交换后:" << endl;
v1.swap(v2);
Print(v1);
Print(v2);
//实际用途
//巧用swap收缩内存空间
vector<int>v;
for (int i = 0; i < 10000; i++)
{
v.push_back(i);
}
cout << "capacity:" << v.capacity() << endl;
cout << "size:" << v.size() << endl;
v.resize(3); //重新指定大小,size变小之后,capacity不变
cout << "capacity:" << v.capacity() << endl;
cout << "size:" << v.size() << endl;
//巧用swap收缩内存
vector<int>(v).swap(v);
cout << "capacity:" << v.capacity() << endl;
cout << "size:" << v.size() << endl;
功能描述:
函数原型:
vector<int>v;
//利用reserve预留空间
v.reserve(10000);
int cnt = 0;//统计开辟空间的次数
int* p = NULL;
for (int i = 0; i < 10000; i++)
{
v.push_back(i);
if (p != &v[0])//每次重新开辟扩容时,会找到一块新的空间,对应一个新的地址
{
p = &v[0];
cnt++;
}
}
cout << "cnt=" << cnt << endl;