Debug HashMap Iteration | Dataford Interview Questions

Find the error in a HashMap iteration loop using keySet().

Represent each iteration and its events relationally. Treat an iteration as erroneous when a structural map mutation occurs while the keys are being traversed.

Output

Return one row per erroneous iteration with map_name, run_id, mutation_count, and error
Include only iterations with at least one PUT, REMOVE, or CLEAR event
Order by map_name, then run_id

Schema

hash_maps

Column	Type	Description
map_idPK	INT	Unique identifier for the map
map_name	VARCHAR(100)	Name of the map being traversed

iteration_runs

Column	Type	Description
run_idPK	INT	Unique identifier for an iteration
map_id	INT	Map traversed by the iteration
started_at	TIMESTAMP	Iteration start timestamp
completed_at	TIMESTAMP	Iteration completion timestamp

iteration_events

Column	Type	Description
event_idPK	INT	Unique event identifier
run_id	INT	Iteration associated with the event
event_type	VARCHAR(20)	Operation observed during iteration
key_text	VARCHAR(100)	Map key involved in the event

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