My failure was misreading it as most common k rather than max k.
Most common k is super-interesting because it can't be solved in one pass in constant space!
https://en.wikipedia.org/wiki/Streaming_algorithm#Frequent_e...
alt Hacker News
Most common k is super-interesting because it can't be solved in one pass in constant space!
https://en.wikipedia.org/wiki/Streaming_algorithm#Frequent_e...