_170.java

package com.fishercoder.solutions;

import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import java.util.Map;


/**
 * 170. Two Sum III - Data structure design
 * <p>
 * Design and implement a _1 class. It should support the following operations: add and find.
 * <p>
 * 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.
 * <p>
 * For example,
 * add(1); add(3); add(5);
 * find(4) -> true
 * find(7) -> false
 */

//Your _1 object will be instantiated and called as such:
//_1 twoSum = new _1();
//twoSum.add(number);
//twoSum.find(value);
public class _170 {
    private Map<Integer, Integer> map = new HashMap();
    private List<Integer> list = new ArrayList();

    // Add the number to an internal data structure.
    public void add(int number) {
        list.add(number);
        map.put(number, map.getOrDefault(number, 0) + 1);
    }

    // Find if there exists any pair of numbers which sum is equal to the value.
    public boolean find(int value) {
        for (int i = 0; i < list.size(); i++) {
            int val1 = list.get(i);
            int val2 = value - val1;
            if (map.containsKey(val2)) {
                if (val1 == val2) {
                    if (map.get(val2) > 1) return true;
                } else return true;
            }
        }
        return false;
    }
}