Flatten 2D Vector

Background Knowledge

The problem of flattening a 2D vector involves taking a collection of collections (in this case, a 2D vector) and creating an iterator that can traverse each element in a linear fashion. This requires an understanding of iterators, which are objects that enable traversal through all the elements in a collection. In the context of this problem, we need to implement an iterator that supports two key operations: next() and has_next(). The next() operation returns the next element in the collection, while the has_next() operation checks if there are more elements to iterate over.

To tackle this problem, it's essential to have a solid grasp of nested structures, such as 2D vectors or matrices, and how to work with them in code. This includes understanding how to access and manipulate individual elements within the nested structure. Additionally, familiarity with control structures, such as loops and conditional statements, is necessary to implement the logic for traversing the 2D vector and handling the next() and has_next() operations.

In terms of specific concepts, it's helpful to understand the difference between lazy iteration and eager iteration. Lazy iteration involves creating an iterator that only computes the next value when next() is called, whereas eager iteration involves computing all values upfront and storing them in memory. For this problem, a lazy iteration approach is likely more suitable, as it allows for more efficient memory usage, especially when dealing with large 2D vectors.