block2.java

Pair findPairGivingSumUsingMap(int[] numbers, int k){
    Set<Integer> seen = new HashSet<Integer>();
    for(int i = 0; i < numbers.length; i++){
        if(seen.contains(k - numbers[i])){
            return new Pair(numbers[i], k - numbers[i]);
        }
        seen.add(numbers[i]);
    }

    return null;
}