_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
 *
 * 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
 */

public class _170 {
  public static class Solution1 {
    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;
    }
  }
}