Merge pull request TheAlgorithms#274 from gabrielangelo/master

hash functions added

Author: harshildarji

data_structures/hashing/__init__.py

@@ -0,0 +1,6 @@
+from .hash_table import HashTable
+
+class QuadraticProbing(HashTable):
+
+    def __init__(self):
+        super(self.__class__, self).__init__()

data_structures/hashing/double_hash.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python3
+
+from .hash_table import HashTable
+from number_theory.prime_numbers import next_prime, check_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 check_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 _colision_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

data_structures/hashing/hash_table.py

@@ -0,0 +1,84 @@
+#!/usr/bin/env python3
+from number_theory.prime_numbers import next_prime
+
+
+class HashTable:
+    """
+        Basic Hash Table example with open addressing and linear probing
+    """
+
+    def __init__(self, size_table, charge_factor=None, lim_charge=None):
+        self.size_table = size_table
+        self.values = [None] * self.size_table
+        self.lim_charge = 0.75 if lim_charge is None else lim_charge
+        self.charge_factor = 1 if charge_factor is None else charge_factor
+        self.__aux_list = []
+        self._keys = {}
+
+    def keys(self):
+        return self._keys
+
+    def balanced_factor(self):
+        return sum([1 for slot in self.values
+                    if slot is not None]) / (self.size_table * self.charge_factor)
+
+    def hash_function(self, key):
+        return key % self.size_table
+
+    def _step_by_step(self, step_ord):
+
+        print("step {0}".format(step_ord))
+        print([i for i in range(len(self.values))])
+        print(self.values)
+
+    def bulk_insert(self, values):
+        i = 1
+        self.__aux_list = values
+        for value in values:
+            self.insert_data(value)
+            self._step_by_step(i)
+            i += 1
+
+    def _set_value(self, key, data):
+        self.values[key] = data
+        self._keys[key] = data
+
+    def _colision_resolution(self, key, data=None):
+        new_key = self.hash_function(key + 1)
+
+        while self.values[new_key] is not None \
+                and self.values[new_key] != key:
+
+            if self.values.count(None) > 0:
+                new_key = self.hash_function(new_key + 1)
+            else:
+                new_key = None
+                break
+
+        return new_key
+
+    def rehashing(self):
+        survivor_values = [value for value in self.values if value is not None]
+        self.size_table = next_prime(self.size_table, factor=2)
+        self._keys.clear()
+        self.values = [None] * self.size_table #hell's pointers D: don't DRY ;/
+        map(self.insert_data, survivor_values)
+
+    def insert_data(self, data):
+        key = self.hash_function(data)
+
+        if self.values[key] is None:
+            self._set_value(key, data)
+
+        elif self.values[key] == data:
+            pass
+
+        else:
+            colision_resolution = self._colision_resolution(key, data)
+            if colision_resolution is not None:
+                self._set_value(colision_resolution, data)
+            else:
+                self.rehashing()
+                self.insert_data(data)
+
+

data_structures/hashing/hash_table_with_linked_list.py

@@ -0,0 +1,24 @@
+from .hash_table import HashTable
+from collections import deque
+
+
+class HashTableWithLinkedList(HashTable):
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+    def _set_value(self, key, data):
+        self.values[key] = deque([]) if self.values[key] is None else self.values[key]  
+        self.values[key].appendleft(data)
+        self._keys[key] = self.values[key]
+
+    def balanced_factor(self):
+        return sum([self.charge_factor - len(slot) for slot in self.values])\
+               / self.size_table * self.charge_factor
+    
+    def _colision_resolution(self, key, data=None):
+        if not (len(self.values[key]) == self.charge_factor
+                and self.values.count(None) == 0):
+            return key
+        return super()._colision_resolution(key, data)
+
+

data_structures/hashing/number_theory/__init__.py

@@ -0,0 +1,29 @@
+#!/usr/bin/env python3
+"""
+    module to operations with prime numbers
+"""
+
+
+def check_prime(number):
+        """
+            it's not the best solution
+        """
+        special_non_primes = [0,1,2]
+        if number in special_non_primes[:2]:
+            return 2
+        elif number == special_non_primes[-1]:
+            return 3
+            
+        return all([number % i for i in range(2, number)])
+
+
+def next_prime(value, factor=1, **kwargs):
+    value = factor * value
+    first_value_val = value
+    
+    while not check_prime(value):
+        value += 1 if not ("desc" in kwargs.keys() and kwargs["desc"] is True) else -1
+    
+    if value == first_value_val:
+        return next_prime(value + 1, **kwargs)
+    return value

data_structures/hashing/number_theory/prime_numbers.py

@@ -0,0 +1,26 @@
+#!/usr/bin/env python3
+
+from .hash_table import HashTable
+
+
+class QuadraticProbing(HashTable):
+    """
+        Basic Hash Table example with open addressing using Quadratic Probing 
+    """
+    def __init__(self, *args, **kwargs):
+        super().__init__(*args, **kwargs)
+
+    def _colision_resolution(self, key, data=None):
+        i = 1
+        new_key = self.hash_function(key + i*i)
+
+        while self.values[new_key] is not None \
+                and self.values[new_key] != key:
+            i += 1
+            new_key = self.hash_function(key + i*i) if not \
+                self.balanced_factor() >= self.lim_charge else None
+
+            if new_key is None:
+                break
+
+        return new_key