mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-10-16 18:51:14 +00:00
c909da9b08
* pre-commit: Upgrade psf/black for stable style 2023 Updating https://github.com/psf/black ... updating 22.12.0 -> 23.1.0 for their `2023 stable style`. * https://github.com/psf/black/blob/main/CHANGES.md#2310 > This is the first [psf/black] release of 2023, and following our stability policy, it comes with a number of improvements to our stable style… Also, add https://github.com/tox-dev/pyproject-fmt and https://github.com/abravalheri/validate-pyproject to pre-commit. I only modified `.pre-commit-config.yaml` and all other files were modified by pre-commit.ci and psf/black. * [pre-commit.ci] auto fixes from pre-commit.com hooks for more information, see https://pre-commit.ci --------- Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
53 lines
1.9 KiB
Python
53 lines
1.9 KiB
Python
#!/usr/bin/env python3
|
|
"""
|
|
Double hashing is a collision resolving technique in Open Addressed Hash tables.
|
|
Double hashing uses the idea of applying a second hash function to key when a collision
|
|
occurs. The advantage of Double hashing is that it is one of the best form of probing,
|
|
producing a uniform distribution of records throughout a hash table. This technique
|
|
does not yield any clusters. It is one of effective method for resolving collisions.
|
|
|
|
Double hashing can be done using: (hash1(key) + i * hash2(key)) % TABLE_SIZE
|
|
Where hash1() and hash2() are hash functions and TABLE_SIZE is size of hash table.
|
|
|
|
Reference: https://en.wikipedia.org/wiki/Double_hashing
|
|
"""
|
|
from .hash_table import HashTable
|
|
from .number_theory.prime_numbers import is_prime, next_prime
|
|
|
|
|
|
class DoubleHash(HashTable):
|
|
"""
|
|
Hash Table example with open addressing and Double Hash
|
|
"""
|
|
|
|
def __init__(self, *args, **kwargs):
|
|
super().__init__(*args, **kwargs)
|
|
|
|
def __hash_function_2(self, value, data):
|
|
next_prime_gt = (
|
|
next_prime(value % self.size_table)
|
|
if not is_prime(value % self.size_table)
|
|
else value % self.size_table
|
|
) # gt = bigger than
|
|
return next_prime_gt - (data % next_prime_gt)
|
|
|
|
def __hash_double_function(self, key, data, increment):
|
|
return (increment * self.__hash_function_2(key, data)) % self.size_table
|
|
|
|
def _collision_resolution(self, key, data=None):
|
|
i = 1
|
|
new_key = self.hash_function(data)
|
|
|
|
while self.values[new_key] is not None and self.values[new_key] != key:
|
|
new_key = (
|
|
self.__hash_double_function(key, data, i)
|
|
if self.balanced_factor() >= self.lim_charge
|
|
else None
|
|
)
|
|
if new_key is None:
|
|
break
|
|
else:
|
|
i += 1
|
|
|
|
return new_key
|