Design and implement an efficient algorithm

Design and implement an efficient algorithm that gives a set of S of an intergers and another x, determines whether or not there exist two elements in S whose sum is exactly x

Using Java

State the analysis for the running time of this approach. (Best case and worst Case)

1 Solve this problem by checking all possible pairs of elements

2 solve this problem by using a more efficient algorithm that does not require checking all possible pairs of elements