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) -> truefind(7) -> false

1 public class TwoSum { 2     private HashMap
     
       map = new HashMap
      
       (); 3     /** Initialize your data structure here. */ 4     public TwoSum() { 5          6     } 7      8     /** Add the number to an internal data structure.. */ 9     public void add(int number) {10         map.put(number, map.containsKey(number) ? map.get(number) + 1 : 1);11     }12     13     /** Find if there exists any pair of numbers which sum is equal to the value. */14     public boolean find(int value) {15         for (Map.Entry
       
         entry : map.entrySet()) {16             int base = entry.getKey();17             int findMe = value - base;18             19             if ((base == findMe && map.get(base) >= 2) || 20                  base != findMe && map.containsKey(findMe))21                  return true;22         }23         return false;24     }25 }26 27 /**28  * Your TwoSum object will be instantiated and called as such:29  * TwoSum obj = new TwoSum();30  * obj.add(number);31  * boolean param_2 = obj.find(value);32  */