C++ —— 关于vector-CFANZ编程社区

(constructor)构造函数声明	接口说明
vector()	无参构造
vector（size_type n, const value_type& val = value_type()）	构造并初始化n个val
vector (const vector& x);	拷贝构造
vector (InputIterator ﬁrst, InputIterator last);	使用迭代器进行初始化构造

2. vector的构造

//模版类只能显式实例化
vector<int> v1;
vector<int> v2(10, 1);

//迭代器初始化
vector<int> v3(v2.begin(), v2.end());
vector<int> v4(++v2.begin(), --v2.end());

3. vector 的遍历

void test_vector1()
{
	vector<int> v1;
	vector<int> v2(10, 1);

	vector<int> v3(++v2.begin(), --v2.end());

    //下标遍历
	for (size_t i = 0; i < v3.size(); i++)
	{
		cout << v3[i] << " ";
	}
	cout << endl;

    //迭代器遍历
	vector<int>::iterator it = v3.begin();
	while (it != v3.end())
	{
		cout << *it << " ";
		++it;
	}
	cout << endl;

    // 范围 for 遍历
	for (auto e : v3)
	{
		cout << e << " ";
	}
	cout << endl;
}

4. vector 的扩容机制

void TestVectorExpend()
{
	size_t sz;
	vector<int> v;
	sz = v.capacity();
	cout << "capacity changed :" << sz << "\n";
	cout << "make a grow" << endl;
	for (size_t i = 0; i < 100; i++)
	{
		v.push_back(i);
		if (sz != v.capacity())
		{
			sz = v.capacity();
			cout << "capacity changed :" << sz << "\n";
		}
	}
}

5. vector 的空间接口

size	获取数据个数
capacity	获取容量大小
empty	判断是否为空
resize	改变vector的size
reserve	改变vector的capacity

5.1 resize 接口

vector<int> v(10, 1);
cout << v.size() << endl;
cout << v.capacity() << endl;

//小于size
v.resize(5, 2);
cout << v.size() << endl;
cout << v.capacity() << endl;
 
//大于size
v.resize(15, 2);
cout << v.size() << endl;
cout << v.capacity() << endl;


void test_vector3()
{
    //10个整形数据1
	vector<int> v(10, 1);
    //申请20空间
	v.reserve(20);
	cout << v.size() << endl;
	cout << v.capacity() << endl;

    //10个整形数据1，补上5个整形数据2
	v.resize(15, 2);
	cout << v.size() << endl;
	cout << v.capacity() << endl;

    //10个整形数据1，5个整形数据2，补上10个整形数据3
	v.resize(25, 3);
	cout << v.size() << endl;
	cout << v.capacity() << endl;
    
    //只保留5个数据
	v.resize(5);
	cout << v.size() << endl;
	cout << v.capacity() << endl;
}

通常 vector 支持迭代器插入

5.2 push_back

//尾插
vector<int> v(10, 1);
v.push_back(10);
for (auto e : v)
{
	cout << e << " ";
}
cout << endl;

5.3 insert

//头插
vector<int> v(10, 1);
v.insert(v.begin(), 1);
for (auto e : v)
{
	cout << e << " ";
}
cout << endl;

//第一个数+3之后在第三个位置进行插入
v.insert(v.begin() + 3, 1);
for (auto e : v)
{
	cout << e << " ";
}

5.4 erase

//头删
vector<int> v(10, 1);
v.erase(v.begin());
for (auto e : v)
{
	cout << e << " ";
}
cout << endl;

//第一个数+3之后删除第三个位置的数据
v.erase(v.begin() + 3);
for (auto e : v)
{
	cout << e << " ";
}
cout << endl;

5.5 流插入与流提取

vector<int> v(10);
for (size_t i = 0; i < v.size(); i++)
{
	cin >> v[i];
}
for (auto e : v)
{
	cout << e << " ";
}
cout << endl;

6. vector 的不同类型元素


	//二维数组
    //5个元素的一维数组
	vector<int> v(5, 1);
    //开辟一个10行5列的二维数组
	vector<vector<int>> vv(10, v);

    vv[2][1]=1;
    //这两段代码的意思是相同的
    //vv.operator[](2)operator[](1)=2;

遍历

 
	//二维数组
    //5个元素的一维数组
	vector<int> v(5, 1);
    //开辟一个10行5列的二维数组
	vector<vector<int>> vv(10, v);

	//使用下标遍历二维数组
	for (int i = 0; i < vv.size(); i++)
	{
		for (int j = 0; j < v.size(); j++)
		{
			cout << vv[i][j] << " ";
		}
		cout << endl;
	}

感谢观看~