Two Sum III - Data Structure Design
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 private HashMap<Integer, Integer> map = new HashMap<Integer, Integer>(); 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<Integer, Integer> 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 */