Two Sum Data Structure

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

Solution

public class TwoSum {

    private static Map<Integer, Integer> map = new HashMap<>();

    public static void add(int number) {
        if(map.containsKey(number))
            map.put(number, map.get(number) + 1);
        else
            map.put(number, 1);
    }

    public static boolean find(int value) {
        for(Integer i: map.keySet()) {
            int target = value - i;
            if(map.containsKey(target)) {
                if(i == target && map.get(i) < 2)
                    continue;
                return true;
            }
        }
        return false;
    }
}