>Einar,
>
>> for i = 1 to alen(myarray)
>> for j = 1 to alen(myarray)
>> if myarray(i)+myarray(j) = X
>> return i,j
>> endi
>> next j
>> next
>
>Your algorithm works but it is quadratic, not linear. A linear algorithm would read each array element once and possibly store one or two values in a variable (hint).
>
>Daniel

Idea:

test = arr[int(k/2)]
if X < test && We don't need to check the rest of the array
   test = arr[int(k/4))
   if X < test && we don't need to check 3/4 of the array
      ...
   endif
endif