170. Two Sum III

https://leetcode.com/problems/two-sum-iii-data-structure-design/description/

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

Sol:

 

public class TwoSum {

    /** Initialize your data structure here. */
    /*
    public TwoSum() {
        
    }
    */
    
    private HashMap<Integer, Integer> map = new HashMap<Integer, Integer>();
    
    
    
    /** Add the number to an internal data structure.. */
    public void add(int number) {
        map.put(number, map.containsKey(number) ? map.get(number) + 1 : 1);
        
    }
    
    /** Find if there exists any pair of numbers which sum is equal to the value. */
    public boolean find(int value) {
        for (Map.Entry<Integer, Integer> entry : map.entrySet()){
            int i = entry.getKey();
            int j = value - i;
            if (i == j && entry.getValue() > 1 || (i != j && map.containsKey(j))){
                return true;
            }
        }
        return false;
        
    }
}

/**
 * Your TwoSum object will be instantiated and called as such:
 * TwoSum obj = new TwoSum();
 * obj.add(number);
 * boolean param_2 = obj.find(value);
 */