动态分配2D数组而不使用任何循环？ [英] Dynamically allocate 2D array without using any loops?

问题描述

我们可以动态分配二维数组，而不使用任何for循环或while循环？
i在c c ++中有任何直接命令或函数？

Can we dynamically allocate 2D array without using any for loop or while loops? i there any direct command or function in c c++?

推荐答案

c ++即一维的大小必须在编译时确定。然后这个分配可以在单个语句中完成，如下所示：

Without using a loop you will have one restriction in ISO c++ i.e. size of one dimension has to be determined at compile time. Then this allocation can be done in a single statement as follows:

#define COLUMN_SIZE 10 // this has to be determined at compile time
int main()
{
    int (* arr)[COLUMN_SIZE];
    int rows = 20; // this is dynamic and can be input from user at run time
    arr = new int[rows][COLUMN_SIZE];
    arr[3][4] = 10;
    cout << arr[3][4] << endl;
    return 0;
}

分配给新的内存需要释放。此外，如果我们将其扩展到n维，则可以在运行时确定这些维度中的只有一个。原因是编译器必须知道每行的大小才能创建一行连续的内存。

The memory allocated with new needs to be freed. Also if we extend it to n dimensions, only one of these dimensions can be determined at run time. The reason is that compiler has to know the size of each row in order to create a row of contiguous memory.

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