title: finding an index i such that a[i] = i
body: <blockquote>
    <p><strong>Possible Duplicate:</strong><br>
    <a href="https://stackoverflow.com/questions/4172580/interview-question-search-in-sorted-array-x-for-index-i-such-that-xi-i">Interview question - Search in sorted array X for index i such that X[i] = i</a>  </p>
  </blockquote>
  
  
  
  <p>You are given with a sorted array of integer and the length of array. Now you have to find an index <code>i</code> such that <code>a(i)=i</code>.
  I am able to do it in o(logn) if index is given but what about if index <code>i</code> is not mentioned?</p>