Two sum

Two sum is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

Task

Given a sorted array of single positive integers, is it possible to find a pair of integers from that array that sum up to a given sum? If so, return indices of the two integers or an empty array if not.

Example

Given numbers = [0, 2, 11, 19, 90], sum = 21,
Because numbers[1] + numbers[3] = 2 + 19 = 21,
return [0, 3].

Source

Stack Overflow: Find pair of numbers in array that add to given sum

C#

<lang csharp>public static int[] TwoSum(int[] numbers, int sum) {

   var map = new Dictionary<int, int>();
   for (var i = 0; i < numbers.Length; i++)
   {
      	var key = sum - numbers[i];
      	if (map.ContainsKey(key))
           return new[] { map[key], i };
       map.Add(numbers[i], i);
   }
   return Array.Empty<int>();

}</lang>

Output:

[0,3]

ooRexx

<lang oorexx>a=.array~of(0, 2, 11, 19, 90) x=21 do i=1 To a~items

 If a[i]>x Then Leave
 Do j=i+1 To a~items
   s=a[i]
   s+=a[j]
   Select
     When s=x Then Leave i
     When s>x Then Leave j
     Otherwise Nop
     End
   End
 End

If s=x Then Do

 i-=1            /* array a's index sarts with 1, so adjust */
 j-=1
 Say '['i','j']'
 End

Else

 Say '[] - no items found'</lang>

Output:

[1,3]