没有新的动态数组（C ++） [英] Dynamic array without new (C++)

问题描述

我是C ++的新手，这是一个非常基本的问题。

I'm new to C++ and this is a very basic question.

在C ++中，只有两种方法来创建动态数组（读一本书，如果我写错了，请更正） 要么是 new 运算符，要么是 malloc（）函数，该函数取自C。

In C++ there are only two ways to create dynamic arrays (read in a book, correct me if I'm wrong) using memory allocation either by new operator or malloc() function which is taken from C.

声明数组 int array [size] 时，方括号 [] 必须具有 const 。

When declaring an array int array[size], the square brackets [] must have a const.

但是在以下代码中， size 是 unsigned int 变量。

However in the following code size is an unsigned int variable.

#include<iostream>

int main() {
    using namespace std;
    unsigned int size;
    cout<<"Enter size of the array : ";
    cin>>size;
    int array[size]; // Dynamically Allocating Memory
    cout<<"\nEnter the elements of the array\n";
    // Reading Elements
    for (int i = 0; i < size; i++) {
        cout<<" :";
        cin>>array[i];
    }
    // Displaying Elements
    cout<<"\nThere are total "<<size<<" elements, as listed below.";
    for (int j = 0; j < size; j++) {
        cout<<endl<<array[j];
    }
    return 0;
}

虽然编译g ++不会出错，而且程序运行正常。

While compiling g++ throws no error and moreover the program runs perfectly.

问题1：这可能是创建动态数组的另一种方法吗？

Question 1 : Could this be another way to create dynamic array?

问题2：代码正确吗？

问题3 ：：如果 [] 仅包含 const ，为什么代码起作用？

Question 3 : If [] can only contain const, why does the code work?

推荐答案

1. 正确，您发现了 a gcc 扩展名。在C中已经允许了很长时间，但是直到C ++ 14才使它成为C ++标准。


2. 是的，假设您还不错，代码是正确的使用该语言的非便携式扩展。


3. 对于符合标准的编译器，这是正确的。您可以通过提供 -std = c ++ 98 或<来告诉 gcc 您不想使用扩展名code> -std = c ++ 11 编译器标志。

1. Correct, you have discovered a gcc extension. This has been allowed in C for a long time, but it has not made it into C++ standard until the C++14.
2. Yes, the code is correct, assuming that you are fine with using non-portable extensions to the language.
3. This is true about standard-compliant compilers. You can tell gcc that you do not want to use extensions by supplying a -std=c++98 or -std=c++11 compiler flag.

如果需要动态C ++中的数组大小，更好的方法是使用 std :: vector< T> 。它为您提供了动态分配数组的灵活性，并为您管理分配的内存。

If you need a dynamically-sized array in C++, a better approach would be to use std::vector<T>. It gives you the flexibility of dynamically allocated array, and takes care of managing the allocated memory for you.

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