我可以使用C ++中的指针访问二维数组的元素吗？ [英] Can I access elements of a 2D array using pointers in C++?

问题描述

对于1D数组，我可以使用数组名作为指针，并添加偏移量来访问数组的每个元素。是否有类似2D数组的东西？

我定义了一个二维数组如下：

  int arr [2] [3] = {{1,2,3}，{4,5,6}}; 
 
 int ** arrPtr = arr; 
  

但是我遇到了第二行的编译错误。应该不是二维数组有类型 int ** ？

C ++在指针访问值的二维数组

，并看到：

  2dArray = new int * [size]; 
  

有人可以告诉我 int * [size] 意味着？ （ size 是 int ，我假设）。

非常感谢。

解决方案

定义为yours的多维数组只是一个指针， 。因此，您可以执行下列操作：

  int arr [2] [3] = {{1,2,3} {4,5,6}}; 
 int * arrPtr =（int *）arr; 
  

一般来说，指向的元素的指针arr [a] [b ] 可以通过 arrPtr + a * bSize + b 访问，其中bSize是第一个数组维度的大小（在这种情况下为三）。

您的第二个问题涉及动态内存分配 - 在运行时分配内存，而不是在程序启动时定义固定金额。我建议您在处理动态分配的2D数组之前，先查看 cplusplus.com 上的动态内存分配。

For 1D array, I can use array name as a pointer and add offset to it to access each element of the array. Is there something similar for 2D arrays?

I defined a 2D array as follows

int arr[2][3] = {{1,2,3}, {4,5,6}};

int** arrPtr = arr;

but I got compiler error for the second line. Shouldn't 2D array have type int**?

I came across another thread here:

C++ Accessing Values at pointer of 2D Array

and saw this:

2dArray = new int*[size];

Could someone please tell me what int*[size] means? (size is an int, I presume).

Thanks a lot.

解决方案

A multidimensional array defined as yours is is only a single pointer, because the data is encoded in sequence. Therefore, you can do the following:

int arr[2][3]={{1,2,3},{4,5,6}};
int* arrPtr = (int*)arr;

In general, the pointer to the element at arr[a][b] can be accessed by arrPtr + a*bSize + b where bSize is the size of the first array dimension (in this case three).

Your second question relates to dynamic memory allocation - allocating memory at runtime, instead of defining a fixed amount when the program starts. I recommend reviewing dynamic memory allocation on cplusplus.com before working with dynamically allocated 2D arrays.

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