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Practice › LeetCode › LeetCode (archived) › LeetCode 06xx ›

LeetCode 601: Human Traffic of Stadium

Problem Restatement We are given a table called Stadium . Each row records one stadium visit day. The table has three columns: Column Type Meaning id int Visit id visit_date date Date of the visit people int Number of people who visited We need to return all rows that are part of a group of at least three consecutive id values where every row has people >= 100 . The...

Programming › Algorithm Cookbook › Chapter 5. Hashing and Maps ›

5.9 Grouping Keys

5.9 Grouping Keys Problem You need to partition items into groups according to a derived key. A counting map records how many times each key appears. A grouping map records the actual items associated with each key. This is useful when the later algorithm needs to process each group separately. Solution Use a map from group key to list of items. groups: Map<Key, List<Item>> For each item, compute its group...