How work this code?

Question

int arr[] = {1, 2, 3, 4, 5, 6, 7, 8, 9};
int size = *(&arr + 1) - arr;

Answer 1

You shouldn't have written any code in Relevant Tags section. Instead, you should use it to specify which language be involved, and optionally some other words that helps describe the problem.

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Answer 2

https://www.geeksforgeeks.org/how-to-find-size-of-array-in-cc-without-using-sizeof-operator/
https://www.geeksforgeeks.org/whats-difference-between-array-and-array-for-int-array5/