安裝中文字典英文字典辭典工具!
安裝中文字典英文字典辭典工具!
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- Hash size: Are prime numbers near powers of two a poor choice for the . . .
This answer possibly explains why choosing M(table size) equal to a power of 2 should be avoided Prime numbers that are too close to a power of 2 will provide the same kind of biasing as a power of 2 for the keys which differs by $+a$ or $-a$ if $2^k=a(modulo)M$
- 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
- 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 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
- why not just use a random number generator as a hash function?
If I understand the question correctly, the answer is simple: if Hash(object) returns 27 when you call it this afternoon, we want Hash(object) to return 27 if we call it next week, on a different computer If you use a random number generator in such a way that this is guaranteed, then go for it
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