title: Looking for appropriate data structures
body: <p>I have data in the following form:</p>
  
  <pre><code>  1-&gt;  (2,3),(4,5),(6,7),(8,2)      //up to 10000 values
    9-&gt;  (4,5),(7,90),(8,1),(9,10)    //up to 1000000 values
    11-&gt; (9,10),(11,2),(12,1)
    ...
  </code></pre>
  
  <p>I want a data structure suitable for quickly finding a value from two keys: the row and the column, so <code>find(9, 7)</code> should give <code>90</code> from the example above.</p>
  
  <p>Note that the value sequences are already sorted, and that I'm more interested in lookup time than insert time.</p>