title: Dictionary in C++ using a Map with no values, only keys
body: <p>I'm implementing some sort of lookup for words in c++, and while the code for implementing a map is there, I wanna make sure if it works that using a map with keys and values as std::string, and using only keys as lookups without a value to return. </p>
  
  <pre><code>    std::vector&lt; std::string&gt; DictionLines;
      Reader DictionReader(Dictionary);
      DictionLines = DictionReader.getLines();
      std::map&lt;std::string, std::string&gt; DictionaryM;
  
      for (int t = 0; t &lt; DictionLines.size(); ++t) {
          DictionaryM.insert(std::pair&lt;std::string, std::string&gt;(DictionLines.at(t), DictionLines.at(t)));
      }
  </code></pre>
  
  <p>This code takes in the 349900 words in a Dictionary.txt file, and stores them in the map. Each line of the dictionary is just the word to lookup; no definition or any value to associate. Which is why I think just storing a pair of the same key and value in the map is ok, and using find and first/second would also be fine? Please confirm.</p>