vector< int>之间的区别是什么? v(N)和向量<整数> v [N]? [英] what is difference between vector<int> v(N) and vector < int > v [N]?

问题描述

什么是vector< int > v(N)?

1. 这是一个最大大小为N的数组(例如vector<int> v)吗?

与vector<int> v[N]一样吗?

我认为这是第一个(如果我错了，请纠正我).

I think it is the first one(correct me if I am wrong).

什么是vector< vector< int > > V(N)?它像最大尺寸为N的2D阵列吗? vector < int > v[N]和vector< vector< int > >v(N)有什么区别?

What is vector< vector< int > > V(N)? Is it like 2D array with maximum size N? What is the difference between vector < int > v[N] and vector< vector< int > >v(N)?

推荐答案

假设

• N是某种整数，
• 某处有一个#include <vector>，
• 某处有using namespace std;或using std::vector; ...

• N is some kind of integer,
• there is an #include <vector> somewhere,
• there is either a using namespace std; or a using std::vector; somewhere...

这是类型为std::vector< int >的对象v的声明，已初始化为保存N对象(类型为int的对象)，这些对象已默认初始化(即不确定，因为int为没有定义默认初始化的POD类型.

This is the declaration of an object v, of type std::vector< int >, initialized to hold N objects (of type int), which are default-initialized (i.e., indeterminate, since int is a POD type for which no default initialization is defined).

vector构造函数的文档 –这种情况(2).

Documentation of vector constructors -- this one is case (2).

螺旋规则-需要适应C ++，但仍然适用良好的开端.

Spiral rule -- which needs some adapting to C++ but is still a good start.

它不是不是动态数组行vector v"，它是 向量.

It is not "a dynamic array line vector v", it is a vector.

不，它与vector v[N](甚至无法编译)相同. 也 不与vector<int> v[N]相同-它是由N个不同的vector<int>对象组成的数组.

And no, it is not the same as vector v[N] (which would not even compile). It is also not the same as vector<int> v[N] -- that would be an array of N different vector<int> objects.

现在，如果它是第一个，那么vector< vector< int > > V(N)是什么?

由于它不是第一个，所以我还必须回答吗? :-D

Since it's not the first one, do I still have to answer this? :-D

vector< vector< int > > V(N);

这是类型为vector< vector< int > >的对象V的声明，即"int-vectors的向量"，已初始化为保存N默认初始化的对象...

That is the declaration of an object V of type vector< vector< int > >, i.e. "vector of int-vectors", initialized to hold N default-initialized objects...

...即，一个包含vector< int >个N个对象的向量-依次为空(因为空"是默认初始化的向量).

...i.e., a vector holding N objects of vector< int > -- which are, in turn, empty (because "empty" is what default-initialized vectors are).

C ++具有...

C++ has...

• 数组(int v[N];)，其工作原理与C数组完全相同.
• std :: vector (std::vector< int > v;)，其大小是动态的.
• std :: array (std::array< int, N >;)，它的大小像C数组一样是静态的，但确实提供了std::vector的一些优点.

• The array (int v[N];), which works exactly like the C array.
• The std::vector (std::vector< int > v;), which is dynamic in size.
• The std::array (std::array< int, N >;), which is static in size like the C array, but does offer some of the niceties of std::vector.

您需要准确地指代您所指的内容.这些是非常独特的类型，具有独特的功能集.

You need to be exact about what you are referring to. These are quite distinct types with a distinct feature set.

更新:

最近几次修改后，很明显您的真实问题是:

With your latest couple of edits, it became clear that your real question is:

什么是vector?

这是一个C ++类模板，实现了一个容器，该容器可以容纳给定类型( like C数组)的连续元素，但是具有动态大小( C数组).

It's a C++ class template implementing a container that can hold contiguous elements of a given type (like a C array), but is dynamically-sized (unlike a C array).

请参阅文档.

通常来说，除了某些 really 特殊情况外，您不再在C ++代码中使用C数组.您将std::string用于字符串，并将std::vector用于(几乎)在C中使用数组的其他所有功能.

Generally speaking, you don't use C arrays in C++ code anymore, except for some really special cases. You use std::string for strings, and std::vector for (almost) everything else you used arrays for in C.

这篇关于vector< int>之间的区别是什么? v(N)和向量<整数> v [N]?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！