You have several ways to express the same traversal. Choose the one that makes the business rule clear, then verify its behavior on the fresh data in each task. These scenarios combine the range predicates, ordered transformations, grouping, merging and Optional operations from this unit. They introduce no new library feature.
The mistakes are in the contracts: a lower bound can be inclusive, repeats can represent separate stock movements, and a blank label can trigger a fallback while an empty preferred token remains present. Read the requested result before choosing a familiar pipeline. Use the hints after trying the edge case yourself. The grouped-count task continues to use the supported list-size equivalent for the browser library.