content: package question0884_uncommon_words_from_two_sentences;
  
  import java.util.ArrayList;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  
  /**
   * 哈希表。
   *
   * 时间复杂度和空间复杂度均是O(n)，其中n为字符串A和B中的单词总数。
   *
   * 执行用时：5ms，击败78.15%。消耗内存：36.2MB，击败89.24%。
   */
  public class Solution {
      private List<String> list = new ArrayList<>();
  
      public String[] uncommonFromSentences(String A, String B) {
          Map<String, Integer> map1 = getMap(A), map2 = getMap(B);
          selectUncommonWords(map1, map2);
          selectUncommonWords(map2, map1);
          String[] result = new String[list.size()];
          for (int i = 0; i < list.size(); i++) {
              result[i] = list.get(i);
          }
          return result;
      }
  
      private void selectUncommonWords(Map<String, Integer> map1, Map<String, Integer> map2) {
          for (String s : map1.keySet()) {
              if (map1.get(s) == 1 && !map2.containsKey(s)) {
                  list.add(s);
              }
          }
      }
  
      private Map<String, Integer> getMap(String s) {
          String[] strings = s.split(" ");
          Map<String, Integer> map = new HashMap<>();
          for (String tmp : strings) {
              if (map.containsKey(tmp)) {
                  map.put(tmp, map.get(tmp) + 1);
              } else {
                  map.put(tmp, 1);
              }
          }
          return map;
      }
  }
  