How can we find out in which element in an array the address and value came from in c++

Question

For example: int a[4] = {2, 4, 34}

Lets say the address of a[0] is at 2000 and we know the value of the element at a[0] is 2.

Given only a memory address and a value of an element, is it possible to determine the position of the element in the array?

If so, please provide an example on how to do this.

Answer 1

Is this what you are looking for? Just using some pointer arithmetic;

int main ()
{
    int ary[] = { 1, 2, 3, 5 };

    int * address_of_2 = &ary[ 1 ];

    int index_of_2 = address_of_2 - ary;

    return 0;
}