Find all pairs of integers within an array which sum to a specified value

Question

Design an algorithm to find all pairs of integers within an array which sum to a specified value.

I have tried this problem using a hash

Answer 1

A solution that takes into account duplicates and uses every number only one time:

void printPairs(int[] numbers, int S) {
    // toMap(numbers) converts the numbers array to a map, where
    // Key is a number from the original array
    // Value is a count of occurrences of this number in the array
    Map numbersMap = toMap(numbers); 

    for (Entry entry : numbersMap.entrySet()) {
      if (entry.getValue().equals(0)) {
        continue;
      }
      int number = entry.getKey();
      int complement = S - number;
      if (numbersMap.containsKey(complement) && numbersMap.get(complement) > 0) {
      for (int j = 0; j < min(numbersMap.get(number), 
                              numbersMap.get(complement)); j++) {
        if (number.equals(complement) && numbersMap.get(number) < 2) {
           break;
        }
        System.out.println(number, complement);
        numbersMap.put(number, numbersMap.get(number) - 1);
        numbersMap.put(complement, numbersMap.get(complement) - 1);
      }
    }
  }
}