题目描述：

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:

1. 0 <= A.length <= 200
2. 0 <= B.length <= 200
3. A and B both contain only spaces and lowercase letters.

解题思路：

使用unordered_map<string，int>记录每个单词出现的次数，次数为一的单词加入返回的vector。

代码：

1 class Solution { 2 public: 3     vector
     
       uncommonFromSentences(string A, string B) { 4         istringstream sin1(A); 5         istringstream sin2(B); 6         string word; 7         unordered_map
      
        words; 8         vector
       
         res; 9         while (sin1>>word) {10             words[word]++;11         }12         while (sin2>>word) {13             words[word]++;14         }15         for (auto iter = words.begin(); iter != words.end(); ++iter) {16             if (iter->second == 1) {17                 res.push_back(iter->first);18             }19         }20         return res;21     }22 };