How does this array element access syntax work?

Question

#include <stdio.h>

int main()
{
    int a[] = {1, 2, 3};

    printf("%d", 0[a]);
    printf("\n%d", 2[a]);

    return 0;
}

Output:

1
3

I know how to access the array element with the index, but how this above syntax accessing the first value in both scenarios and add the prefixed numbers?

https://stackoverflow.com/questions/5073350/accessing-arrays-by-indexarray-in-c-and-c — Tharun K, Feb 23 '21 at 05:14

score 3 · Accepted Answer · answered Feb 23 '21 at 05:14

In C, the arrays and pointers have similarities. When you access an array element array[3]. This is equivalent to:

*(array + 3) // Dereferencing the 3rd index from beginning

Similarly, when you try to access it like 3[array], the statement goes like:

*(3 + array) // Identical to the first example

Which is identical. Lastly, when you want to obtain the N-th element of an array N[array], the syntax becomes:

*(N + array)

That's why you get your expected output.

How does this array element access syntax work?

1 Answers1