Implement a reverse hash table

Question

Sigiloso · Accepted Answer

As a way to make it as space-conserving as possible, the key->value pair can be inserted at the hashes of both the key and value. This would allow you to both differentiate a forward and reverse lookup, and use only a single additional pointer of space per entry.

Sigiloso · Answer

This was easy enough but I somehow had seen this done with just one hash table and that isn't really possible. Should have gone with the simple, direct approach and optimized later.

Razvan · Answer

Can you be more precise regarding the meaning of a "reverse hash table"

Sigiloso · Answer

Say its a table T like this:

T[1] = "Bob"
T[2] = "Sally"
T[3] = "Greg"

Then it should also be possible to do:

T["Bob"] = 1
T["Sally"] = 2
T["Greg"] = 3

Keys can be values and values can be used as keys

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