Care to search for integers that sum?

I spent the better part of yesterday pondering how to efficiently search a sorted array of integers to see if a pair of integers within the array sum to given integer.

i.e., given the numbers 1, 2, 3, 5, 8, 13 -- does any pair of them add up to 8 (yes: 3+5), 13 (yes: 5+8), or 17 (no)?

There's several ways to solve this problem, but the trick is to do it in linear time (only visit each number in the array once) and linear space (don't make any copies of the numbers in the array).

After giving it the old college try, I searched for the proper algorithm and found it.

Here's the resulting Java:

public class IntsForSumJava {

 public static boolean doIntsForSumExist(int[] inputs, int target_sum) {
   int start_idx = 0;
   int end_idx = inputs.length - 1;
   boolean found_target = false;
   int iterations = 0;

   while (!found_target) {
     iterations++;
     int start = inputs[start_idx];
     int end = inputs[end_idx];
     if (end == (target_sum - start)) {
       found_target = true;
     } else if (end > (target_sum - start)) {
       end_idx--;
       if (end_idx > end_idx) {
         break;
       }
     }
   }
   System.out.println("iterations: " + iterations);
   return found_target;
 }

 public static void main(String[] args) {
   int[] inputs = {1, 2, 3, 5, 8, 13};
   int target_sum = 0;
   System.out.println("found target (" + target_sum + "): " +
       IntsForSumJava.doIntsForSumExist(inputs, target_sum));
   target_sum = 8;
   System.out.println("found target (" + target_sum + "): " +
       IntsForSumJava.doIntsForSumExist(inputs, target_sum));
   target_sum = 13;
   System.out.println("found target (" + target_sum + "): " +
       IntsForSumJava.doIntsForSumExist(inputs, target_sum));
   target_sum = 17;
   System.out.println("found target (" + target_sum + "): " +
       IntsForSumJava.doIntsForSumExist(inputs, target_sum));
 }
}

Just in case you were wondering...

Happy searching.