[Hash Map / Set, Easy] Find the Difference of Two Arrays

https://leetcode.com/problems/find-the-difference-of-two-arrays/description/?envType=study-plan-v2&envId=leetcode-75

딱히 설명 필요 없을 듯

class Solution {
    public List<List<Integer>> findDifference(int[] nums1, int[] nums2) {
        Set<Integer> nums1Set = new HashSet<>();
        Set<Integer> nums2Set = new HashSet<>();

        for (int n : nums1) {
            nums1Set.add(n);
        }
        for (int n : nums2) {
            nums2Set.add(n);
        }

        List<Integer> nums1List = new ArrayList<>(nums1Set);
        nums1List.removeAll(nums2Set);

        List<Integer> nums2List = new ArrayList<>(nums2Set);
        nums2List.removeAll(nums1Set);

        List<List<Integer>> answer = new ArrayList<>();
        answer.add(nums1List);
        answer.add(nums2List);

        return answer;
    }
}