Two Sum III - Data structure design

170. 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  
public class TwoSum {  
    Map<Integer, Integer> map;

    /** Initialize your data structure here. */
    public TwoSum() {
        map = new HashMap<>();
    }

    /** Add the number to an internal data structure.. */
    public void add(int number) {
        if (map.containsKey(number)) {
            map.put(number, map.get(number) + 1);
        } else {
            map.put(number, 1);
        }
    }

    /** Find if there exists any pair of numbers which sum is equal to the value. */
    public boolean find(int value) {
        for (int i : map.keySet()) {
            int target = value - i;

            if (map.containsKey(target)) {
                if (target != i) {
                    return true;
                } else {
                    if (map.get(i) > 1) {
                        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);
 */

Hope this helps,
Michael