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

5.10 Composite Keys

5.10 Composite Keys Problem You need to use multiple fields together as a single key in a hash table. Examples include (user_id, timestamp) , (x, y) coordinates, (source, destination) , or (name, version) . Treating each field separately leads to incorrect grouping or lookup. Treating them together requires a consistent definition of equality and hashing. Solution Define a composite key type with equality and hashing over all relevant fields. Key:...

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

5.2 Hash Functions

5.2 Hash Functions Problem You need a function that turns a key into a hash code so that a hash table can place the key into a bucket. A hash table depends on two operations. First, it must decide whether two keys are equal. Second, it must compute a hash code for each key. These two operations must agree. Whenever two keys are equal, they must produce the same hash...