title: Can a string be formed by erasing only a single character from another string
body: <p>Suppose I have two strings A and B. I have to figure out whether string a can be made by erasing only a single character from B.</p>
  
  <p>I have a <code>O(n)</code> solution to it. But can it be done in <code>O(log(n))</code> or <code>O(1)</code>? Any hints?</p>