LeetCodeExercise4

class Solution {
    Set<Integer> hashSet = new HashSet<>();
    public int singleNumber(int[] nums) {
        int sum1 =0;
        int sum2 =0;
        for(int i : nums){
            if(!hashSet.contains(i)){
                sum1+=i;
                hashSet.add(i);
                System.out.print("this the hashet now " + hashSet);
            }
            sum2+=i;
        }
        return (int)2*sum1 - sum2;        
    }
}