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Search found 2359 results on 95 pages for 'hash'.

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• Constructing a hash table/hash function.

  - by nn

  Hi, I would like to construct a hash table that looks up keys in sequences (strings) of bytes ranging from 1 to 15 bytes. I would like to store an integer value, so I imagine an array for hashing would suffice. I'm having difficulty conceptualizing how to construct a hash function such that given the key would give an index into the array. Any…

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• Problem with hash function: hash(1) == hash(1.0)

  - by mtasic

  I have an instance of dict with ints, floats, strings as keys, but the problem is when there are a as int and b as float, and float(a) == b, then their hash values are the same, and thats what I do NOT want to get because I need unique hash vales for this cases in order to get corresponding values. Example: d = {1:'1', 1.0:'1.0', '1':1,…

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• Are hash collisions with different file sizes just as likely as same file size?

  - by rwmnau

  I'm hashing a large number of files, and to avoid hash collisions, I'm also storing a file's original size - that way, even if there's a hash collision, it's extremely unlikely that the file sizes will also be identical. Is this sound (a hash collision is equally likely to be of any size), or do I need another piece of information (if a…

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• Hash table vs Hash list vs Hash tree?

  - by Passionate programmer

  What property makes Hash table, Hash list and Hash tree different from each other? Which one is used when? When is table superior than tree.

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• Refactoring this code that produces a reverse-lookup hash from another hash

  - by Frank Joseph Mattia

  This code is based on the idea of a Form Object http://blog.codeclimate.com/blog/2012/10/17/7-ways-to-decompose-fat-activerecord-models/ (see #3 if unfamiliar with the concept). My actual code in question may be found here: https://gist.github.com/frankjmattia/82a9945f30bde29eba88 The code takes a hash of objects/attributes and…

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• Are has collisions with different file sizes just as likely as same file size?

  - by rwmnau

  I'm hashing a large number of files, and to avoid hash collisions, I'm also storing a file's original size - that way, even if there's a hash collision, it's extrememly unlikely that the file sizes will also be identical. Is this sound (a hash collision is equally likely to be of any size), or do I need another piece of…

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• Why it is called "hash table", or "hash function"? Hash doesn't make any sense to me here

  - by Saeed Neamati

  It's now about 4 years of development that I'm using, hearing, talking about, and implementing hash tables and hash functions. But I really never understand why it's called hash? I remember the first days I started programming, this term was kind'of cumbersome terminology to me. I never figured out what is it, based on…

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• How to quickly generate a new string hash after concatenating 2 strings

  - by philcolbourn

  If my math is right, I can quickly generate a new hash value for the concatenation of two strings if I already have the individual hash values for each string. But only if the hash function is of the form: hash(n) = k * hash(n-1) + c(n), and h(0) = 0. In this case, hash( concat(s1,s2) ) = k**length(s2) * hash(s1) +…

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• Create a Sorted Hash in Java with a Custom Comparator

  - by kunjaan

  I want to create a TreeMap in Java with a custom sort order. The sorted keys which are string need to be sorted according to the second character. The values are also string. Sample Hash: Za,FOO Ab,Bar

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• What is a hash function in java?

  - by Mohit Deshpande

  I have check out this Wikipedia page on it, but I still don't understand it. Can someone please help my dim-witted mind to understand the concepts of hashing, hashtable/hashmap, and hash functions? Some examples would really help.

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• Hash of unique value = unique hash?

  - by Nebs

  Theoretically does hashing a unique value yield a unique value? Let's say I have a DB table with 2 columns: id and code. id is an auto-incrementing int and code is a varchar. If I do ... $code = sha1($id); ... and then store $code into the same row as $id. Will my code column be unique as well? What about if I…

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• perl: added hash entry in a subroutine is lost

  - by hansi

  Why is the hash empty on the second call of printHash? my %hash = (); addToHash(\%hash); printHash(\%hash); sub addToHash { my %hash = %{$_[0]}; $hash{"test"} = "test"; printHash(\%hash); } sub printHash { print "printHash: \n"; my %hash = %{$_[0]}; foreach my $key (keys %hash) { print "key:…

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• md5sum returns a different hash value than online hash generators

  - by Ravi

  On suse10, md5sum myname gives md5 hash as 49b0939cb2db9d21b038b7f7d453cd5d The file myname contains string "ravi" while some of the online md5 hash generators for the same string seem to give a different hash http://md5-encryption.com/ http://www.miraclesalad.com/webtools/md5.php They spit out the hash for…

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• EMERGENCY - Major Problems After Perl Module Installed via WHM

  - by Russell C.

  I attempted to install the perl module Net::Twitter::Role::API::Lists using WHM and after doing so my whole site came down. It seems that something that was updated with the install isn't functioning correctly and since our website it written in Perl none of our site scripts will run. In almost 8 years of…

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• Objective-C : Fowler–Noll–Vo (FNV) Hash implementation

  - by Dough

  Hi ! I have a HTTP connector in my iPhone project and queries must have a parameter set from the username using the Fowler–Noll–Vo (FNV) Hash. I have a Java implementation working at this time, this is the code : long fnv_prime = 0x811C9DC5; long hash = 0; for(int i = 0; i < str.length(); i++) { …

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• Why do we need Hash by key? [migrated]

  - by Royi Namir

  (i'm just trying to find what am I missing...) Assuming John have a clear text message , he can create a regular hash ( like md5 , or sha256) and then encrypt the message. John can now send Paul the message + its (clear text)hash and Paul can know if the message was altered. ( decrypt and then compare…

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• Time complexity to fill hash table (homework)?

  - by Heathcliff

  This is a homework question, but I think there's something missing from it. It asks: Provide a sequence of m keys to fill a hash table implemented with linear probing, such that the time to fill it is minimum. And then Provide another sequence of m keys, but such that the time fill it is…

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• Heaps of Trouble?

  - by Paul White NZ

  If you’re not already a regular reader of Brad Schulz’s blog, you’re missing out on some great material.  In his latest entry, he is tasked with optimizing a query run against tables that have no indexes at all.  The problem is, predictably, that performance is not very good.  The…

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• Perl Hash Slice, Replication x Operator, and sub params

  - by user210757

  Ok, I understand perl hash slices, and the "x" operator in Perl, but can someone explain the following code example from here (slightly simplified)? sub test{ my %hash; @hash{@_} = (undef) x @_; } Example Call to sub: test('one', 'two', 'three'); This line is what throws…

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• 3 hash functions to best hash sliding window strings for a bloom filter with minimum collisions

  - by Duaa

  Hi all: I need 3 hash functions to hash strings of a sliding window moving over a text, to be used later to search within a bloom vector. I'm using C# in my programming I read something about rolling hash functions and cyclic polynomials, they are used for sliding window applications. But…

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• Standard way to hash an RSA key?

  - by Adam J.R. Erickson

  What's the algorithm for creating hash (sha-1 or MD5) of an RSA public key? Is there a standard way to do this? Hash just the modulus, string addition of both and then take a hash? Is SHA-1 or MD5 usually used? I want to use it to ensure that I got the right key (have the sender send a…

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• reference to specific hash key

  - by dave

  How do I create a reference to the value in a specific hash key. I tried the following but $$foo is empty. Any help is much appreciated. $hash->{1} = "one"; $hash->{2} = "two"; $hash->{3} = "three"; $foo = \${$hash->{1}}; $hash->{1} = "ONE"; #I want "MONEY: ONE"; print…

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• Oracle Hash Cluster Overflow Blocks

  - by Andrew

  When inserting a large number of rows into a single table hash cluster in Oracle, it will fill up the block with any values that hash to that hash-value and then start using overflow blocks. These overflow blocks are listed as chained off the main block, but I can not find detailed…

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• From string to hex MD5 hash and back

  - by Pablo Fernandez

  I have this pseudo-code in java: bytes[] hash = MD5.hash("example"); String hexString = toHexString(hash); //This returns something like a0394dbe93f bytes[] hexBytes = hexString.getBytes("UTF-8"); Now, hexBytes[] and hash[] are different. I know I'm doing something wrong…

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• Strange ruby behavior when using Hash.new([])

  - by Valentin Vasilyev

  Consider this code: h=Hash.new(0) #new hash pairs will by default have 0 as values h[1]+=1 # {1=>1} h[2]+=2 # {2=>2} that's all fine, but: h=Hash.new([]) #empty array as default value h[1]<<=1 #{1=>[1]} - OK h[2]<<=2 #{1=>[1,2], 2=>[1,2]} # why ??…

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