title: Implementation of hash table using unordered_map in c++ and handling collisions
body: <p>How to implement a hash map using unordered map in c++.
  If the keys in unordered map corresponds to the index generated by the hashing function,
  what when there are multiple values have same keys( collision). Then how do we access these values using the same keys.</p>
  
  <p>eg</p>
  
  <pre><code>unordered_map &lt;int,string&gt; hashTable;
  
  hashTable.insert(pair&lt;int,string&gt;(3,"ab"))
  hashTable.insert(pair&lt;int,string&gt;(3,"ba"))
  </code></pre>
  
  <p>Now how do access "ba"?</p>