find的version1 版本注意num2Occur 需定义为Integer类型,建议version2版本
[ref]
https://leetcode.com/discuss/19515/my-solutions-java-and-python-time-for-add-time-for-find-space
public class TwoSum { private HashMap<Integer, Integer> map = new HashMap<Integer, Integer>(); public void add(int number) { map.put(number, map.containsKey(number) ? 2 : 1); } // version 2 public boolean find(int value) { for (Integer num1 : map.keySet()) { int num2 = value - num1; if (map.containsKey(num2) && (map.get(num2) == 2 || num1 != num2)) return true; } return false; } // version 1 public boolean find1(int value) { for (Integer num1 : map.keySet()) { Integer num2Occur = map.get(value - num1); if (num2Occur != null && (num2Occur == 2 || num1 != (value - num1))) return true; } return false; } } // Version 1: TLE // public class TwoSum { // private HashSet<Integer> sumSet; // private HashSet<Integer> numSet; // public TwoSum() { // sumSet = new HashSet<Integer>(); // numSet = new HashSet<Integer>(); // } // public void add(int number) { // if (!numSet.isEmpty()) { // for (int item : numSet) // sumSet.add(item + number); // } // numSet.add(number); // } // public boolean find(int value) { // return sumSet.contains(value); // } // }