title: find max between two indices of unsorted array in O(1) time
body: <p>In an un sorted array, (we can pre-process this array). How can we answer the following query in O(1) time?     Find the maximum from index i to j</p>
  
  <p><strong>Edit:</strong> The preprocessing can take O(n) time and O(n) order of extra memory, so that the query which comes too often is answered in O(1) time...</p>