Find the difference between two set - Cracking Code

Find the difference between two set – Cracking Code
找出两个数组的差，比如A = [1,1,1,2,2,2], B= [2,2,3]，在A出现在B不出现的集合是[1,1,1,2]， 在B出现在A 不出现的集合是[3]

1. public static void main(String[] args) {
2. List<Integer> A = new ArrayList<>(Arrays.asList(1,1,1,2,2,2));
3. List<Integer> B = new ArrayList<>(Arrays.asList(2,2,3));
4. System.out.println(findSubset(B, A));
5. System.out.println(findSubset(A, B));
6. }
7. public static List<Integer> findSubset(List<Integer> A, List<Integer> B) {
8. List<Integer> result = new ArrayList<>();
9. if (A.size() == 0) return result;
10. if (B.size() == 0) {
11. result.addAll(A);
12. return result;
13. }
14. HashMap<Integer, Integer> map = new HashMap<>();
15. for (int num : A) {
16. map.put(num, map.getOrDefault(num, 0) + 1);
17. }
18. for (int num : B) {
19. if (map.containsKey(num)) {
20. map.put(num, map.get(num) - 1);
21. }
22. }
23. for (int num : map.keySet()) {
24. for (int i = 0; i < map.get(num); i++) {
25. result.add(num);
26. }
27. }
28. return result;
29. }

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