c++ stl队列初始化

Here, we have to declare, initialize and access a vector in C++ STL.

在这里，我们必须声明，初始化和访问C ++ STL中的向量。

向量声明 (Vector declaration)

Syntax:

句法：

 vector<data_type> vector_name;

Since, vector is just like dynamic array, when we insert elements in it, it automatically resize itself.

由于vector就像动态数组一样，当我们在其中插入元素时，它会自动调整大小。

We can also use, the following syntax to declare dynamic vector i.e a vector without initialization,

我们还可以使用以下语法声明动态向量，即不初始化的向量 ，

vector<data_type> vector_name{};

If, we want to initialize a vector with initial elements, we can use following syntax,

如果要使用初始元素初始化向量，则可以使用以下语法，

vector<data_type> vetor_name{elements};

矢量迭代器 (Vector iterator)

To access/iterate elements of a vector, we need an iterator for vector like containers. We can use following syntax to declare a vector iterator:

要访问/迭代向量的元素，我们需要一个类似容器的向量迭代器。 我们可以使用以下语法来声明向量迭代器：

 vector<data_type>::iterator iterator_name;

Example:

例：

vector<int>::iterator it;

vector :: begin()和vector :: end()函数 (vector:: begin() and vector::end() functions )

Function vector::begin() return an iterator, which points to the first element in the vector and the function vector::end() returns an iterator, which points to the last element in the vector.

函数vector :: begin()返回一个迭代器，该迭代器指向向量中的第一个元素，函数vector :: end()返回一个迭代器，该迭代器指向向量中的最后一个元素。

Program 1: Declare vector with Initialization and print the elements

程序1：使用初始化声明矢量并打印元素

#include <iostream>
#include <vector>
using namespace std;
int main() {
// declare vector with 5 elements 
vector<int> num{10, 20, 30, 40, 50} ;
//print the elements - to iterate the elements,
//we need an iterator 
vector<int>::iterator it;
//iterate and print the elements
cout<< "vector (num) elements: ";
for( it=num.begin(); it!=num.end() ; it++ )
cout<< *it << " ";
return 0;
}

Output

输出量

    vector (num) elements: 10 20 30 40 50 

Program 2: Declare a vector without initialization, insert some elements and print

程序2：在不初始化的情况下声明向量，插入一些元素并打印

To insert elements in vector, we use vector::push_back() – this is a predefined function, it insert/pushes the elements at the end of the vector.

要在vector中插入元素，我们使用vector :: push_back() –这是一个预定义的函数，它将在矢量末尾插入/推送元素。

#include <iostream>
#include <vector>
using namespace std;
int main() {
// declare vector 
vector<int> num{};
//insert elements
num.push_back (100);
num.push_back (200);
num.push_back (300);
num.push_back (400);
num.push_back (500);
//print the elements - to iterate the elements,
//we need an iterator
vector<int>::iterator it;
//iterate and print the elements
cout<< "vector (num) elements: ";
for(it=num.begin (); it !=num.end (); it++ )
cout<< *it << " ";
return 0;
}

Output

输出量

    vector (num) elements: 100 200 300 400 500 

翻译自: https://www.includehelp.com/stl/declare-initialize-and-access-a-vector.aspx

c++ stl队列初始化