kaetzacoatl - 2 months ago 4
C Question

# Initialize only some values of an array

This might be a stupid question, but is it possible to assign some values to an array instead of all? To clarify what I want:

If I need an array like

`{1,0,0,0,2,0,0,0,3,0,0,0}`
I can create it like:

``````int array[] = {1,0,0,0,2,0,0,0,3,0,0,0};
``````

Most values of this array are '0'. Is it possible to skip this values and only assign the values 1, 2 and 3? I think of something like:

``````int array[12] = {0: 1, 4: 2, 8: 3};
``````

Is it possible to skip this values and only assign the values 1, 2 and 3?

In C, Yes. Use designated initializer (added in C99 and not supported in C++).

``````int array[12] = {[0] = 1, [4] = 2, [8] = 3};
``````

Above initializer will initialize element `0`, `4` and `8` of array `array` with values `1`, `2` and `3` respectively. Rest elements will be initialized with `0`. This will be equivalent to

`````` int array[12] = {1, 0, 0, 0, 2, 0, 0, 0, 3, 0, 0, 0};
``````

The best part is that the order in which elements are listed doesn't matter. One can also write like

`````` int array[12] = {[8] = 3, [0] = 1, [4] = 2};
``````

But note that the expression inside `[ ]` shall be an integer constant expression.

Source (Stackoverflow)