# Questions tagged [hash]

Mathematical function that maps arbitrarily-sized data to fixed-size integers, often used as keys in hash tables or to help ensure data integrity

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### Detecting and correcting collisions in (Zorbist) hashing to avoid errors in transposition table

Context Say I have a transposition table that uses keys produced by (e.g. Zorbist) hashing game positions. The table has a finite recycled memory (key % p is the <...
1answer
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### Avoid Storing Keys in Key-Value Store by Replacing the Key with 128-bit Murmur3 Hash

I want to develop LRU key-value data store and in that wanted to get rid of space to store the key itself. Instead wanted to store a 128 bit murmur hash. The structure of data-store that I want to ...
1answer
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### Count Sketch probability bound

I have been reading up on the Count Sketch algorithm, and I stumpled upon the Count Sketh algorithm explained in section 5 of https://www.cs.dartmouth.edu/~ac/Teach/data-streams-lecnotes.pdf. Then, I ...
1answer
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### Universal hash function for strings of unbounded length

Is there a (weakly) universal hash function for strings without any assumption of the string length? I did not find one on Google / Wikipedia.
0answers
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### Finding the longest power subsequence

A power sequence is a sequence containing consecutive powers of a number starting from power one. for example $3^1, 3^2, 3^3$ is a power sequence. The question is to find the length of the longest ...
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1answer
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### How can I prove or disprove that the following function is bijection?

For a research project, I tried to prove or disprove that a function called xxhash128_low is a bijection from 64 bit unsigned integer to 64 bit unsigned integer. I have shown that it is sufficient to ...
3answers
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### Integer set disjointness query on sketches with something like homomorphic hashing

Suppose I have two sets of integers $A$ and $B$ and I have a sketch data structure described by a function $\mathsf{sketch}_n : \mathcal{P}(\mathbb{Z}) \to 2^n$ that returns a bitstring of size $n$. ...
2answers
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1answer
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### Separate Chaining hashing: time complexity of successful search

In a simple uniform hashing with chaining collision, the time complexity of a successful search is: $Θ(1 + (1 + \frac{α}{2} - \frac{α}{2n}))$ where $α=\frac{n}{m}$, but I don't understand how to ...
1answer
53 views

### Formal definition of hash function

I was reading through the classic CLRS with the intention of reviewing the hash tables theory, more specifically the hash function definition I just wanted a reference to quote. I cannot find a ...
0answers
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### How to generate unique keys for different two dimensional matrices having different sizes?

No. of rows in the table (as given in image) is not known beforehand . The problem I am dealing with generates different 2-D matrices based on the input data given. As soon as a matrix generates it ...