mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-11-24 05:21:09 +00:00
36 lines
871 B
Python
36 lines
871 B
Python
|
"""
|
||
|
|
This algorithm (k=33) was first reported by Dan Bernstein many years ago in comp.lang.c
|
||
|
|
Another version of this algorithm (now favored by Bernstein) uses xor:
|
||
|
|
hash(i) = hash(i - 1) * 33 ^ str[i];
|
||
|
|
|
||
|
|
First Magic constant 33:
|
||
|
|
It has never been adequately explained.
|
||
|
|
It's magic because it works better than many other constants, prime or not.
|
||
|
|
|
||
|
|
Second Magic Constant 5381:
|
||
|
|
|
||
|
|
1. odd number
|
||
|
|
2. prime number
|
||
|
|
3. deficient number
|
||
|
|
4. 001/010/100/000/101 b
|
||
|
|
|
||
|
|
source: http://www.cse.yorku.ca/~oz/hash.html
|
||
|
|
"""
|
||
|
|
|
||
|
|
|
||
|
|
def djb2(s: str) -> int:
|
||
|
|
"""
|
||
|
|
Implementation of djb2 hash algorithm that
|
||
|
|
is popular because of it's magic constants.
|
||
|
|
|
||
|
|
>>> djb2('Algorithms')
|
||
|
|
3782405311
|
||
|
|
|
||
|
|
>>> djb2('scramble bits')
|
||
|
|
1609059040
|
||
|
|
"""
|
||
|
|
hash = 5381
|
||
|
|
for x in s:
|
||
|
|
hash = ((hash << 5) + hash) + ord(x)
|
||
|
|
return hash & 0xFFFFFFFF
|