hash

Python frozenset hashing algorithm / implementation

由 让人想犯罪 __ 提交于 2019-12-28 12:02:10
问题 I'm currently trying to understand the mechanism behind the hash function defined for Python's built-in frozenset data type. The implementation is shown at the bottom for reference. What I'm interested in particular is the rationale for the choice of this scattering operation: lambda h: (h ^ (h << 16) ^ 89869747) * 3644798167 where h is the hash of each element. Does anyone know where these came from? (That is, was there any particular reason to pick these numbers?) Or were they simply chosen

String similarity score/hash

由 纵饮孤独 提交于 2019-12-28 07:39:10
问题 Is there a method to calculate something like general "similarity score" of a string? In a way that I am not comparing two strings together but rather I get some number (hash) for each string that can later tell me that two strings are or are not similar. Two similar strings should have similar (close) hashes. Let's consider these strings and scores as an example: Hello world 1000 Hello world! 1010 Hello earth 1125 Foo bar 3250 FooBarbar 3750 Foo Bar! 3300 Foo world! 2350 You can see that

MD5 hash with different results

由 耗尽温柔 提交于 2019-12-28 05:58:56
问题 Im trying to encode some chains to MD5 but I have noticed that: For the chain: "123456çñ" Some webs like http://www.md5.net www.md5.cz md5generator.net return: "66f561bb6b68372213dd9768e55e1002" And others like: http://www.adamek.biz/md5-generator.php 7thspace.com/webmaster_tools/online_md5_encoder.html md5.rednoize.com/ return: "9e6c9a1eeb5e00fbf4a2cd6519e0cfcb" I'd need to encode the chains with standar md5 because I need to connect my results with other systems. which hash is the correct?

What is the best way to create a random hash/string?

由 北战南征 提交于 2019-12-28 05:04:08
问题 What is the best way of generating a hash for the purpose of storing a session? I am looking for a lightweight, portable solution. 回答1: You can use PHP's built-in hashing functions, sha1 and md5. Choose one, not both. One may think that using both, sha1(md5($pass)) would be a solution. Using both does not make your password more secure, its causes redundant data and does not make much sense. Take a look at PHP Security Consortium: Password Hashing they give a good article with weaknesses and

HashMap和HashTable

由 倾然丶 夕夏残阳落幕 提交于 2019-12-28 03:07:00
JAVA的基础知识：数据结构（Map,List,Set等）,设计模式，算法，线程相关，IO/NIO，序列化等等 其次是高级特征：反射机制，并发与锁，JVM（GC策略，类加载机制，内存模型）等等 举个例子 就比如问你：HashMap 是不是有序的？ 你回答不是有序的。那面试官就会可能继续问你，有没有有序的Map实现类呢？ 你如果这个时候说不知道的话，那这块问题就到此结束了。如果你说有TreeMap和LinkedHashMap。 那么面试官接下来就可能会问你，TreeMap和LinkedHashMap是如何保证它的顺序的？ 如果你回答不上来，那么到此为止。 如果你说TreeMap是通过实现SortMap接口，能够把它保存的键值对根据key排序，基于红黑树，从而保证TreeMap中所有键值对处于有序状态。 LinkedHashMap则是通过插入排序（就是你put的时候的顺序是什么，取出来的时候就是什么样子）和访问排序（改变排序把访问过的放到底部）让键值有序。 1、为什么用HashMap？ HashMap是一个散列桶（数组和链表），它存储的内容是键值对(key-value)映射 HashMap采用了数组和链表的数据结构，能在查询和修改方便继承了数组的线性查找和链表的寻址修改 HashMap是非synchronized，所以HashMap很快 HashMap可以接受null键和值

Why aren't Python sets hashable?

由 ☆樱花仙子☆ 提交于 2019-12-28 02:39:36
问题 I stumbled across a blog post detailing how to implement a powerset function in Python. So I went about trying my own way of doing it, and discovered that Python apparently cannot have a set of sets, since set is not hashable. This is irksome, since the definition of a powerset is that it is a set of sets, and I wanted to implement it using actual set operations. >>> set([ set() ]) Traceback (most recent call last): File "<stdin>", line 1, in <module> TypeError: unhashable type: 'set' Is

How does double arrow (=>) operator work in Perl?

由 大城市里の小女人 提交于 2019-12-28 02:07:06
问题 I know about the hash use of the => operator, like this $ cat array.pl %ages = ('Martin' => 28, 'Sharon' => 35, 'Rikke' => 29,); print "Rikke is $ages{Rikke} years old\n"; $ perl array.pl Rikke is 29 years old $ and I thought it was just syntax to initialize hashes, but in answers to How can I qualify a variable as const/final in Perl?, => has been used like this use Readonly; Readonly my $infilename => "input_56_12.txt"; What exactly does => mean? Are there more ways in which => can be used?

Accessing elements of nested hashes in ruby [duplicate]

由 时光怂恿深爱的人放手 提交于 2019-12-27 20:11:16
问题 This question already has answers here : Ruby Style: How to check whether a nested hash element exists (16 answers) How to avoid NoMethodError for nil elements when accessing nested hashes? [duplicate] (4 answers) Closed 3 years ago . I'm working a little utility written in ruby that makes extensive use of nested hashes. Currently, I'm checking access to nested hash elements as follows: structure = { :a => { :b => 'foo' }} # I want structure[:a][:b] value = nil if structure.has_key?(:a) &&

window.location.hash 使用说明

由 时光毁灭记忆、已成空白 提交于 2019-12-27 17:52:26
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> location是javascript里面管理地址栏的内置对象. 比如loation.href是 页面的url .但是 location.hash可以获取或设置页面的 标签值 比如http://domain/#testDemo中 咱们的location.hash 就是 #testDemo 　　下面引用一个 网上的demo 一个搜索版块,功能有3个:普通搜索,高级搜索,后台管理,分别指明他们各自的hash 值:#search,#advsearch,#adminboss. 在页面初始化的时候,通过window.location.hash来判断用户需要访问的页面,也就是将要显示的版块 var hash; hash = (!window.location.hash)?"#search":window.location.hash; window.location.hash = hash; //这里我们解释一下(!window.location.hash)什么意思?首先如果当前页面的地址栏的链接地址 不包含#....的这些的话,直接取值的话,他会为空!比如这个例子,http://www.jb51.net/直接取 alert(window.location.hash)//""空 转化为 boolean值 为 false //

window.location.hash解析

由 泪湿孤枕 提交于 2019-12-27 17:34:48
【推荐】2019 Java 开发者跳槽指南.pdf(吐血整理) >>> location对象：设置或获取当前URL的信息 使用location对象可以设置或返回URL中的一些信息，一个完整的URL地址的格式为： 协议://主机:端口/路径名称#hash标识?搜索条件 其 中，协议是URL的起始部分，用于指定该URL地 址所采用的通信协议，比如http、ftp等；主机是指该URL所对应的服务器的名称；端口用于指定服务器用于通信的端口号，与主机名之间使用冒号隔开； 路径名称是指该URL所对应的网页文件在服务器上的虚拟路径；如果页面中含有锚点连接，可以使用hash标志指定页面中的锚点标志，该标志以“#”开头； 搜索条件是指URL中所含有的查询条件，该查询条件以“?”开头，以“变量名称=值”的形式出现，多个查询条件之间使用连接符“&”连接。比 如：http://upc.edu.cn:8080/wwwroot/ index.html#topicID?id=3876。 利用location对象可以方便地设置或获取URL中的各种信息，本节将详细介绍location对象的一些常用属性和方法。 1．hash属性 【功能说明】设置或获取URL中的锚点名称，如果Web页面中使用的锚点连接，通过设置location对象的hash属性可以方便的跳转到页面中的不同部分。 【基本语法】location.hash
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