Using a for loop to reverse an array does nothing [duplicate]

Question

This question already has an answer here:

• Transpose matrix: swapping elements doesn't alter values 1 answer

I am trying to reverse an array of 15 numbers by using a for loop, but for some reason the array order stays the same.

My code looks like this:

int main()
{
    int arr[15] = { 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 };
    int i, j, temp;
    for (i = 0; i < 15; i++)
    {
        temp = arr[15 - i - 1];
        arr[15 - i - 1] = arr[i];
        arr[i] = temp;
    }
    j = 0;
    do {
        std::cout << arr[j] << " ";
        j++;
    } while (j < 15);
}

Any idea what have I done wrong?

Answer 1

Yes, you swap all the elements back again once i is past the half-way point.

To reverse, you only need to go half way; i.e. run i to 15 / 2.