Leetcode:TwoSumIII-Datastructuredesign

Design and implement a TwoSum class. It should support the following operations: add and find.

add - Add the number to an internal data structure.
find - Find if there exists any pair of numbers which sum is equal to the value.

For example,
add(1); add(3); add(5);
find(4) -> true
find(7) -> false

 1 public class TwoSum {
 2         Set sum;
 3         Set num;
 4         
 5         TwoSum(){
 6             sum = new HashSet();
 7             num = new HashSet();
 8         }
 9         // Add the number to an internal data structure.
10         public void add(int number) {
11             if(num.contains(number)){
12                 sum.add(number * 2);
13             }else{
14                 Iterator iter = num.iterator();
15                 while(iter.hasNext()){
16                     sum.add(iter.next() + number);
17                 }
18                 num.add(number);
19             }
20         }
21     
22         // Find if there exists any pair of numbers which sum is equal to the value.
23         public boolean find(int value) {
24             return sum.contains(value);
25         }
26     }

 1 public class TwoSum {
 2     HashMap map;
 3     public TwoSum() {
 4         map = new HashMap();
 5     }
 6     
 7     public void add(int x) {
 8         if (map.containsKey(x)) {
 9             map.put(x, map.get(x)+1);
10         }
11         else {
12             map.put(x, 1);
13         }
14     }
15     
16     public boolean find(int target) {
17         for (int i : map.keySet()) {
18             if (map.containsKey(target-i)) {
19                 if (target - i != i) return true;
20                 else if (map.get(i) >= 2) return true;
21             }
22         }
23         return false;
24     }
25 }