Balanced string split

int balanced_string_split(const char * str)
{
    int rs, ls, splits = 0;
    const char * cptr;

    while (rs = ls = 0, cptr = str, *str)
    {
        do
        {
            if ('R' == *cptr)
                rs++;
            else
                ls++;

            if (rs == ls)
                splits++;
            else if (2 == rs - ls || -2 == rs - ls)
                break;
        } while (*cptr++);
        str++;
    }
    return splits;
}