Two Sum III - Data structure design @LeetCode

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

	import java.util.HashMap;
	import java.util.Map;
	// case: add(0) -> find(0) -> should be false
	public class TwoSumIII {
	Map<Integer, Integer> dict = new HashMap<Integer, Integer>();
	public void add(int number) {
	if (dict.containsKey(number)) {
	dict.put(number, dict.get(number) + 1);
	} else {
	dict.put(number, 1);
	}
	}
	public boolean find(int value) {
	for (Integer key : dict.keySet()) {
	if (value - key == key) {
	if (dict.get(key) >= 2) {
	return true;
	}
	} else if (dict.containsKey(value - key)) {
	return true;
	}
	}
	return false;
	}
	public static void main(String[] args) {
	TwoSumIII util = new TwoSumIII();
	util.add(1);
	util.add(3);
	util.add(5);
	System.out.println(util.find(4));
	System.out.println(util.find(7));
	}
	}

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