Anyone has a ready implementation of the Reverse Breadth First traversal algorithm in C#?

By Reverse Breadth First traversal , I mean instead of searching a tree starting from a common node, I want to search the tree from the bottom and gradually converged to a common node.

Let's see the below figure, this is the output of a Breadth First traversal :

In my reverse breadth first traversal , 9,10,11 and 12 will be the first few nodes found ( the order of them are not important as they are all first order). 5, 6, 7 and 8 are the second few nodes found, and so on. 1 would be the last node found.

Any ideas or pointers?

Edit: Change "Breadth First Search" to "Breadth First traversal" to clarify the question