> In the real world, you use a well-tested premade off the shelf library to traverse a DAG or implement a red/black tree.
Unless, you know, you are implementing the standard library for a new language, so that there is no such "off the shelf library" available. Which its not been completely unknown for Google software engineers to do.
"Off the shelf libraries" aren't things that are handed down on stone tablets to the prophet on a mountaintop, they are things that are created by software engineers.
In any case, understanding which algorithms and data structures to use, even if you are using a pre-made library, and the impacts of that decision requires an understanding of the algorithms and data structures similar to that which is needed to implement them (it doesn't strictly require the ability to implement, but ability to implement isn't an unreasonable way of filtering for the requisite knowledge.)
Unless, you know, you are implementing the standard library for a new language, so that there is no such "off the shelf library" available. Which its not been completely unknown for Google software engineers to do.
"Off the shelf libraries" aren't things that are handed down on stone tablets to the prophet on a mountaintop, they are things that are created by software engineers.
In any case, understanding which algorithms and data structures to use, even if you are using a pre-made library, and the impacts of that decision requires an understanding of the algorithms and data structures similar to that which is needed to implement them (it doesn't strictly require the ability to implement, but ability to implement isn't an unreasonable way of filtering for the requisite knowledge.)