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+/**
+* We are given two sentences A and B. (A sentence is a string of space separated
+* words. Each word consists only of lowercase letters.)
+*
+* A word is uncommon if it appears exactly once in one of the sentences, and
+* does not appear in the other sentence.
+*
+* Return a list of all uncommon words.
+*
+* You may return the list in any order.
+*
+* Example 1:
+* Input: A = "this apple is sweet", B = "this apple is sour"
+* Output: ["sweet","sour"]
+*
+* Example 2:
+* Input: A = "apple apple", B = "banana"
+* Output: ["banana"]
+*
+* Note:
+* 0 <= A.length <= 200
+* 0 <= B.length <= 200
+* A and B both contain only spaces and lowercase letters.
+*/
+
+public class UncommonWordsFromTwoSentences884 {
+public String[] uncommonFromSentences(String A, String B) {
+Set<String> once = new HashSet<>();
+Set<String> mult = new HashSet<>();
+String[] as = A.split(" ");
+for (String s: as) {
+if (once.contains(s)) {
+once.remove(s);
+mult.add(s);
+} else if (!mult.contains(s)) {
+once.add(s);
+}
+}
+
+String[] bs = B.split(" ");
+Set<String> resCand = new HashSet<>();
+Set<String> resMult = new HashSet<>();
+for (String s: bs) {
+if (!once.contains(s) && !mult.contains(s)) {
+if (resCand.contains(s)) {
+resCand.remove(s);
+resMult.add(s);
+} else if (!resMult.contains(s)) {
+resCand.add(s);
+}
+} else if (once.contains(s)) {
+once.remove(s);
+mult.add(s);
+}
+}
+
+String[] res = new String[resCand.size() + once.size()];
+int i = 0;
+for (String c: resCand) {
+res[i++] = c;
+}
+for (String c: once) {
+res[i++] = c;
+}
+return res;
+}
+
+/**
+* https://leetcode.com/problems/uncommon-words-from-two-sentences/solution/
+*/
+public String[] uncommonFromSentences2(String A, String B) {
+Map<String, Integer> count = new HashMap();
+for (String word: A.split(" "))
+count.put(word, count.getOrDefault(word, 0) + 1);
+for (String word: B.split(" "))
+count.put(word, count.getOrDefault(word, 0) + 1);
+
+List<String> ans = new LinkedList();
+for (String word: count.keySet())
+if (count.get(word) == 1)
+ans.add(word);
+
+return ans.toArray(new String[ans.size()]);
+}
+}