[LeetCode] 170. Two Sum III - Data structure design

Problem

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.

Example 1:

add(1); add(3); add(5);
find(4) -> true
find(7) -> false

Example 2:

add(3); add(1); add(2);
find(3) -> true
find(6) -> false

Solution

class TwoSum {
    Map<Integer, Integer> map;
    public TwoSum() {
        map = new HashMap<>();
    }
    
    public void add(int number) {
        map.put(number, map.getOrDefault(number, 0)+1);
    }
    
    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() >= 2) ||
                (i != j && map.containsKey(j))) {
                return true;
            }
        }
        return false;
    }
}

Two HashSet -- TLE

class TwoSum {

    Set<Integer> nums;
    Set<Integer> sums;
    /** Initialize your data structure here. */
    public TwoSum() {
        nums = new HashSet<>();
        sums = new HashSet<>();
    }
    
    /** Add the number to an internal data structure.. */
    public void add(int number) {
        Iterator<Integer> iterator = nums.iterator();
        while (iterator.hasNext()) {
            sums.add(iterator.next()+number);
        }
        nums.add(number);
    }
    
    /** Find if there exists any pair of numbers which sum is equal to the value. */
    public boolean find(int value) {
        return sums.contains(value);
    }
}