What if array name is put in square brackets?

Question

I saw such a piece of C code:

int main()
{
    static int a[] = {7,8,9};
    printf("%d", 2[a] + a[2]);;
    
    return 0;
}

What does 2[a] mean here?

Answer 1

a[b] and b[a] are 100% equivalent in C. What you have there is a very unidiomatic way of writing a[2].

By way of more complete explanation, array subscript notation a[b] is also 100% equivalent to *(a + b), which may make the reason it works both ways clearer.