什么是“最后一个元素"?在向量中意味着什么? [英] What does"one-past-the-last-element" mean in vectors?

问题描述

我正在学习向量，并且对数组如何复制到这里的向量感到困惑

I'm learning vectors and am confused on how the array is copying to thevector here

double p[] = {1, 2, 3, 4, 5};
std::vector<double> a(p, p+5);

我也知道 std :: vector< double>a(3,5); 的意思是为3腾出空间并用5初始化它们".

I also know std::vector<double> a(3,5); means `make room for 3 and initialize them with 5. How does the above code work?

第二点是我从复制上面的代码的地方阅读了该段.

The second point is I read the paragraph from where I copied the above code.

使用向量或任何其他标准容器.受控顺序始终是以[first，last-past-last)的形式表示-不仅适用于ctor，而且适用于对于在一系列元素上运行的每个函数也是如此.

Understanding the second point is crucial when working with vectors or any other standard containers. The controlled sequence is always expressed in terms of [first, one-past-last)—not only for ctors, but also for every function that operates on a range of elements.

我不知道 [第一个，最后一个)是什么意思?我在数学上知道，但是不知道向量为什么/如何以这种方式复制数组?

I don't know what is the meant by [first, one-past-last) ? I know mathematically but don't know why/how vector copy the array in this way?

已编辑

另一个相关问题

成员函数 end()返回一个迭代器，该迭代器指向"序列中的 last-last-element .请注意，取消引用由 end()返回的迭代器是非法的，并且结果不确定.

The member function end() returns an iterator that "points" to one-past-the-last-element in the sequence. Note that dereferencing the iterator returned by end() is illegal and has undefined results.

您能解释一下最后一个元素是什么吗?为什么?

Can you explain this one-past-the-last-element what is it? and why?

推荐答案

请勿从STL容器中取消引用 end()或 rend()，因为它们不会指向有效元素.
下面的图片可以帮助您形象化.

Never dereference end() or rend() from STL containers, as they do not point to valid elements.
This picture below can help you visualize this.

半开范围的优势是:
1.当begin()== end()
时，将处理空范围2.通过检查直到迭代器等于end()，可以直观地完成元素的迭代.

The advantage of an half open range is:
1. Handling of empty ranges occur when begin() == end()
2. Iterating over the elements can be intuitively done by checking until the iterator equals end().

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