Generating the perfect hash function with a given list of strings?

Question

Suppose I have a list of N lines known at compile time.

I want to generate (at compile time) a function that will display each line in a separate integer from 1 to N inclusive. A function should take up very little time or space to execute.

For example, suppose my lines are:

 {"apple", "orange", "banana"}

Such a function may return:

f("apple") -> 2
f("orange") -> 1
f("banana") -> 3

What is the strategy to create this feature?

I thought to parse strings at compile time and look for a couple of constants that I could put or add, or something else?

Compilation time generation time / space can be quite expensive (but obviously not so funny).

Answer 1

, m , _{i, j} - j- i- . , . , _{i, j} , j & ge; | < > > |.

, , :

• ( ) m - 1 , , .

• -, -m -.

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, - m-1 . . 1 . , : - 1 . , 0 , , , 1 .

, , m - 1 , ( , , log, m). , . . m , , . .

, m - 1 p ₁,..., p _{m - 1}. _{i, p j} p _j & ge; | a _i |: .

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h (a _i) = & sum; _{j = 1} ^{m - 1} [q _j a _{i, p j}% n], q _j n. h -: P (x & ne; y & wedge; h (x) = h (y)) & le; 1/.

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-, -. , m ² h n = m ² , . , , 2, , , .

Answer 2

. 1 , 2 - ,... , .

, trie , .