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- Hash tables versus binary trees - Computer Science Stack Exchange
In particular, if you're going to need the order on the keys, for example if you want to be able to list the keys in alphabetical order, then hash tables are no help (you'll need to sort them), whereas you can straightforwardly traverse a search tree in order You can combine binary search trees and hash tables in the form of hash trees A hash
- 什么是 hash？ - 知乎
整个Hash算法的过程就是把原始任意长度的值空间，映射成固定长度的值空间的过程。 2、Hash的特点 一个优秀的hash算法，需要什么样的要求呢？ a)、从hash值不可以反向推导出原始的数据 这个从上面MD5的例子里可以明确看到，经过映射后的数据和原始数据没有
- hash - What would happen SHA-256 collision were to be found? - Computer . . .
As far as I and this wikipedia page know, there are no collisions (2 inputs with the same output) found in SHA-256 (yet) what would happen if a collision were to be found, 1 would it be easier to
- hash - Do passwords need a max length? - Computer Science Stack Exchange
Hash algorithms are designed to produce a practically random output, so for a 24-byte (192-bit) hash, you'd need on the order of $ 2^{96} $ or $ 10^{30} $ inputs to have an approximately 50 % chance of two of them hashing to the same value Due to passwords usually being composed of letters (or nearly enough) and not arbitrary bytes, the hash
- hash tables - Number of probes in a successful search in open address . . .
Given an open-address hash table with $\alpha$ < 1, the expected number of probes in a successful search is at most $\frac{1}{\alpha}\ln\frac{1}{1-\alpha}$ I read this in a book and the proof starts by saying Searching for k follows the same probe sequence as inserting it
- 到底什么是哈希值，哈希值到底是怎么生成的，有什么用？ - 知乎
hash值是通过一个计算函数把难以比较的字符串或者其他类型的数据映射成一个整数，最常用的就是映射a～z的hash值，变成hash[(str(i)-‘a’]这个数是一个十进制数，这个十进制数把它映射到0-25，也就是数组下标，但通常来说是映射成1-26，因为方便计算，这是最简单的hash值，然后这个hash值映射成下标
- What is the advantage of seperate chaining over open addressing?
The hash nodes are a little bigger, but all of the hash values to check are in the same cache line If you're particularly lucky, the compiler may even turn this into a SIMD operation for you If the hash table is stored on disk, variations of this technique can improve locality much more than open addressing, at the cost of using extra space
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