C ++可以使用可变长度数组，因为我的后续程序工作正常 [英] Does C++ can have variable length array as my following program worked

问题描述

i was told that arrays cant work like this but this has worked for me even with declaring with variable sized array in codeblocks. how so?

我尝试过：

What I have tried:

<pre>#include <iostream>
using namespace std;

int main() {
    int a;
    cin>>a;
   int arr[a];

   for(int i=0;i<a;i++)
   {
       cin>>arr[i];
   }
   cout<<arr[2];
   return 0;
}

推荐答案

这不是可变大小的数组，而是指定数组的大小，

That is not a variable size array, you are specifying the size of the array,

cin >> a;
int arr[a]; // Right here.

尝试做除此之外的任何东西，例如，

Try doing anything other than that, such as,

int arr[5];

cin >> a;

// Try adding this to the array now, 
int arr[a]; // See what happens.

虽然，是的，这是动态大小的数组，但不是可变大小的数组。它们之间存在巨大差异，它们在许多方面都是有用的和有害的。至于存在可变大小的数组，这个概念甚至不存在于其他高级语言中，例如C＃，Java。它们还有容器（List等），用于处理在运行时增长或缩小的集合。



如果你想要一个可变大小的数组，用C ++查找向量。向量是一个可变大小的数组，它由数组支持，但它的大小可以在运行时更改 - 数组的大小不能在运行时更改，仅在创建时指定。



vector - C ++ Reference [ ^ ]

Although, yes, that is a dynamically sized array, but not a variable size array. There is a huge difference in between both of them and, they are both useful and harmful in many ways. As for existence of variable-sized arrays, the concept does not even exist in other high-level languages, such as C#, Java. They also have containers (List, etc.) that take care of the collections that grow or shrink on run-time.

If you want a variable sized array, look for vectors in C++. A vector is a variable sized array, it is backed by an array but its size can change on the runtime — the size of your array cannot be changed on runtime, only specified at creation.

vector - C++ Reference[^]

您可能正在使用支持C ++的GNU编译器：

You are probably using the GNU compiler which supports them for C++:

使用GNU编译器集合（GCC）：可变长度 [ ^ ]：

ISO C99允许使用可变长度自动数组，作为扩展，GCC在C90模式和C ++中接受它们。

Variable-length automatic arrays are allowed in ISO C99, and as an extension GCC accepts them in C90 mode and in C++.

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