The grouping part clicked pretty fast but I fumbled on the score assignment for a bit.
First, traverse the list to identify consecutive runs of Photo items and group every three into a PhotoGroup with the max score. Then, collect all ungrouped items and the new PhotoGroups, sort them by score descending, and return the result. Be sure to handle edge cases like leftover photos and maintain the original order within groups.
Pro tip: Clarify upfront whether the sort should be stable for ties and whether leftover photos (fewer than 3) should remain as individual items. This shows attention to detail and prevents incorrect assumptions.
Ask about tie-breaking in sorting, handling of leftover photos (1 or 2), and whether grouping should reset after non-photo items. Confirm that the original order of photos within a group is preserved.
Iterate through the list, maintaining a buffer of consecutive photos. When the buffer reaches 3, create a PhotoGroup with the max score, clear the buffer, and continue. At the end, any remaining photos in the buffer are treated as individual items.
Gather all non-photo items, leftover photos, and newly created PhotoGroups into a single list. Sort this list by score in descending order, using a stable sort if tie-breaking is unspecified.
Discuss time and space complexity: O(n) for grouping and O(n log n) for sorting, where n is the number of items. Mention that the grouping can be done in a single pass and sorting is the dominant cost.
Walk through a concrete example, such as a list with mixed types and multiple photo runs, to verify the grouping and sorting logic. Include edge cases like no photos, exactly 3 photos, and photos at the end.
AI-generated suggestions, not part of the candidate's original notes. May be inaccurate — verify before relying on them.