Given a tree, prune it to select for only a certain node color
Given that a tree is made of only red or black nodes, return another tree that only has the paths of the original tree leading to a red node.
Problem Statement
Given that a tree is made of only red or black nodes, return another tree that only has the paths of the original tree leading to a red node.
References
Ankur from Google
Recommended reading

Breadth First Tree Traversal
Write an algorithm that takes a tree data structure and writes out all the elements in a breadthfirst traversal order.

Closest Common Ancestor of a Node in a Tree
You have a tree data structure. Write an algorithm that given any two nodes in the tree, finds the node that is the closest common ancestor to them.

Google search results for the top 1000 highest ranking URLs
You have trillions of URLs stored uniquely, without order, across numerous machines, each with a score. Find the 1000 URLs with the highest scores.

Extreme Recursion with Binary Tree Topologies
How many binary tree topologies are possible given n nodes?
 Author
 Amin Ariana
 Published
 April 2011