title: 6-node binary tree, exactly 2 have exactly 1 child
body: <p>Is such a binary tree possible? I've drawn out what I believe to be all possible iterations, and I cannot find a tree that satisfies these properties. Note that this is not a BST, so the values of the keys don't matter. There are countless with exactly 1 "single child" node, such as :</p>
  
  <pre><code>      a
       / \
      b   c
     /          //b is only such node
    d
   / \
  e   f
  </code></pre>
  
  <p>And many with exactly 3 "single child" nodes:</p>
  
  <pre><code>          a
           / 
          b   
         /          //a, b, and d
        c
       / \
      d   e
     /
    f 
  </code></pre>
  
  <p>Does such a binary tree exist (6 nodes, exactly 2 nodes with exactly 1 child)? If so, please provide an example.        </p>