Right, but for most tree problems, you don't need to write your own tree. People should know how to use trees, and when one would use them (a map with ordered

Right, but for most tree problems, you don't need to write your own tree. People should know how to use trees, and when one would use them (a map with ordered traversals.) For graph problems you will often have to write your own graph for the peculiarities of your problem, but the area I work in doesn't really have many graph problems.