STL vector中的rend方法（10）

2023-10-28 15:50

文章标签 方法 vector stl rend

本文主要是介绍STL vector中的rend方法（10），希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！

原文地址:http://www.cplusplus.com/reference/vector/vector/rend/

其实rend和end的区别和rbegin和begin的区别几乎是一样的。

public member function

 <vector> 

std::vector::rend

C++98
C++11

      reverse_iterator rend() noexcept;
const_reverse_iterator rend() const noexcept;

Return reverse iterator to reverse end

Returns a reverse iterator pointing to the theoretical element preceding the first element in the vector (which is considered its reverse end).

返回一个反向的迭代器指向假设中存在于vector第一个元素前面一个位置的元素(这个元素被认为是反转后的尾部)

The range between vector::rbegin and vector::rend contains all the elements of the vector (in reverse order).

范围rbegin和rend之间就包含了vector（倒序）的所有元素。

Parameters

none

Return Value

A reverse iterator to the reverse end of the sequence container.

一个反向迭代器指向一个序列倒序的超尾。

If the vector object is const-qualified, the function returns a const_reverse_iterator. Otherwise, it returns a reverse_iterator.

如果vector对象本身具有const属性，那么该函数返回的将是const_reverse_itertor.

否则，返回一个普通的reverse_iterator.

Member types reverse_iterator and const_reverse_iterator are reverse random access iterator types (pointing to an element and to a const element, respectively). See vector member types.
返回迭代器类型为随机访问迭代器。

Example

// vector::rbegin/rend
#include <iostream>
#include <vector>int main ()
{std::vector<int> myvector (5);  // 5 default-constructed intsstd::vector<int>::reverse_iterator rit = myvector.rbegin();int i=0;for (rit = myvector.rbegin(); rit!= myvector.rend(); ++rit)*rit = ++i;std::cout << "myvector contains:";for (std::vector<int>::iterator it = myvector.begin(); it != myvector.end(); ++it)std::cout << ' ' << *it;std::cout << '\n';return 0;
}

Edit & Run

Output:

5 4 3 2 1

我个人测试的例子：

#include <iostream>
#include <vector>
#include <iterator>
#include <initializer_list>
using namespace std;
int main()
{
vector<int> vi({10,20,30,40});
cout<<"Reverse vector:"<<endl;
for(auto it=vi.rbegin();it!=vi.rend();++it)
cout<<*it<<endl;
auto it2=vi.rend();
cout<<"This is values of rend():"<<*it2<<endl;
it2++;
cout<<"This is values of rend()++:"<<*it2<<endl;
auto it3=vi.rend();
it3--;
cout<<"This is values of rend()--:"<<*it3<<endl;

}

运行结果：

可以看到，如果对rend()返回的迭代器直接解除引用，得到的将是默认的0，只有对其进行递减操作（因为rend()已经是倒序的结尾，要想取得其他元素的值，应该递减）

Complexity

Constant.

Iterator validity

No changes.

Data races

The container is accessed (neither the const nor the non-const versions modify the container).

容器将被访问。（不管是const还是不是，该方法都不会修改容器）

No contained elements are accessed by the call, but the iterator returned can be used to access or modify elements. Concurrently accessing or modifying different elements is safe.
该方法不会访问容器里的元素，但是返回的这个iterator可以用来访问元素，并且用他们来访问或者是修改不同的元素都是安全的。