title: Unordered_map or hashMap existing hash function modify?
body: <p>I used <em><strong>unordered_map&lt;long long int, long long int&gt;</strong></em> <em><strong>the key may take values of upto 1e9</strong></em>, this lead to my answer being Time Limit Exceeded.</p>
  <p>when I used map&lt;long long int, long long int&gt; it was succesful.</p>
  <p>I came to know from  other answers that <strong><em>unordered_map is bad when hash function is bad , is there a way to change the hash function of this unordered_map</em>?</strong></p>