Un profesor me dijo que no debería usar.
int *array = malloc(sizeof *array * length);
And that it should instead be:
int *array = malloc(length * sizeof(int));
Both are valid, but many veteran programmers will prefer the way you did it.
The advantage of using sizeof *array as opposed to sizeof(int) is that if you happen to change the type of array then you don’t need to change how you do the allocation.
There’s also no technical reason to multiply by length first instead of the element size. If anything, when looking at a call to malloc the first thing you want to know is how many “things” you’re allocating, so from a readability standpoint putting the length first might make more sense. On the other hand, because the result of the sizeof operator is unsigned, putting it first guarantees that the math is done with unsigned types if you have multiple array dimensions.
You also don’t want to cast the return value of malloc as that can mask other errors in your code, specifically a missing #include <stdlib.h>