Question

writing a recursive string reverse function out of curiosity, but having a bit of problem with XOR there. The whole point of this function, is to not use iterator, which is why it is a recursive function. this is not homework, just curiosity.

    private static char[] ReverseNL(char[] arr, int index)
    {
        var len = arr.Length;
        if (index > 0)
            arr[len - index] ^= arr[index - 1];
        return index-- < 1 ? arr : ReverseNL(arr, index);
    }

it seems to jamble the first part of my string

“hey there stack!” becomes “I♫→A ←E↨reht yeh”

it is always the first half of the phrase that gets jumbled…

UPDATE..

i suppose XOR wasn’t really needed here.. so used basic assignment, also got rid of return.

    private static void ReverseNL(char[] arr, int index) {
        var len = arr.Length;
        if (index > 0 && index > len / 2) {
            var c = arr[len - index];
            arr[len - index] = arr[index - 1];
            arr[index - 1] = c;
            index--;
            ReverseNL(arr, index);
        }
    }

Answer 1

If you want a solution which uses XOR and recursion, try this:

private static void ReverseNL(char[] arr, int index)
{
    if (index <arr.Length/2)
    {
        arr[index] ^= arr[arr.Length - index-1];
        arr[arr.Length - index-1] ^= arr[index ];
        arr[index] ^= arr[arr.Length - index-1];
        ReverseNL(arr,++index);
    }
}

You don’t need to return anything, since everything is done in the array. Of course you could just remove the XOR-part and just swap the elements, but this is much cooler. 😉

(edit: index should start at 0)