title: Removing duplicates from an array using divide and conquer in O(nlogn) time
body: <p>You are given an Array A of n requests for 2010 olympic tickets. The array is ordered by the time of the request so that A(1) is the first to arrive and A(2) is the second to arrive etc. Each request contains a ten digit telephone number. In order to try to be fair the olympic organizers have made a rule that there can only be one request from each telephone number. It has been noticed that array A contains more than one request from some telephone numbers. Write an O(nlogn) time divide and conquer algorithm to remove from A all requests from the same telephone number except the first received. The final output should be array A containing m&lt;=n requests from a unique telephone number. Also the requests in A should remain in the same order as they were before the duplicates were removed.</p>
  
  <p>I get how this can be done if the array was sorted by telephone number however I do not see how it is possible when the array is sorted by request time.</p>