如何在 C 中使用动态多维数组? [英] How do I work with dynamic multi-dimensional arrays in C?

问题描述

有人知道我如何使用 C 来使用动态分配的多维数组吗?这可能吗?

Does someone know how I can use dynamically allocated multi-dimensional arrays using C? Is that possible?

推荐答案

使用动态分配，使用 malloc:

With dynamic allocation, using malloc:

int** x;

x = malloc(dimension1_max * sizeof(*x));
for (int i = 0; i < dimension1_max; i++) {
  x[i] = malloc(dimension2_max * sizeof(x[0]));
}

//Writing values
x[0..(dimension1_max-1)][0..(dimension2_max-1)] = Value; 
[...]

for (int i = 0; i < dimension1_max; i++) {
  free(x[i]);
}
free(x);

这会分配一个大小为 dimension1_max * dimension2_max 的二维数组.因此，例如，如果您想要一个 640*480 的数组(图像的 fe 像素)，请使用 dimension1_max = 640, dimension2_max = 480.然后您可以访问该数组使用 x[d1]​​[d2] 其中 d1 = 0..639, d2 = 0..479.

This allocates an 2D array of size dimension1_max * dimension2_max. So, for example, if you want a 640*480 array (f.e. pixels of an image), use dimension1_max = 640, dimension2_max = 480. You can then access the array using x[d1][d2] where d1 = 0..639, d2 = 0..479.

但是在 SO 或 Google 上的搜索也揭示了其他可能性，例如 在这个问题中

But a search on SO or Google also reveals other possibilities, for example in this SO question

请注意，在这种情况下，您的数组不会分配连续的内存区域(640*480 字节)，这可能会给假设此的函数带来问题.所以为了让数组满足条件，用这个替换上面的 malloc 块:

Note that your array won't allocate a contiguous region of memory (640*480 bytes) in that case which could give problems with functions that assume this. So to get the array satisfy the condition, replace the malloc block above with this:

int** x;
int* temp;

x = malloc(dimension1_max * sizeof(*x));
temp = malloc(dimension1_max * dimension2_max * sizeof(x[0]));
for (int i = 0; i < dimension1_max; i++) {
  x[i] = temp + (i * dimension2_max);
}

[...]

free(temp);
free(x);

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