Starts implementing a neighbour implementation

02_hash_maps/hm.py

@@ -113,3 +113,49 @@ class HMTableCollision(HashMap):
 			h = (h << 4) + ord(letter)
 			
 		return h % self._hash_size
+
+class HashMapNeighbourCollision():
+	def __init__(self, hash_size=513):
+		self._hash_size = hash_size
+		self._size = 0
+		self.hmap = [None] * self._hash_size
+		
+	def add(self, key, value):
+		"""
+		Adds the provided value to the hashmap.
+		Raises an Exception if a collision is detected
+		"""
+		my_key = self._hash(key)
+		if self.hmap[my_key] == None:
+			self.hmap[my_key] = value
+			self._size += 1
+		else: 
+			raise Exception("Collision detected at index %d", key)
+		
+	def get(self, key):
+		"""
+		Finds the element in the hash table that may contain the id for 
+		the string we are looking for
+		"""
+		my_key = self._hash(key)
+		return self.hmap[my_key]		
+	
+	def size(self):
+		return self._size
+	
+	def _hash(self, value):
+		"""
+		Generates a hash for the given value.
+		The input is expected to be a String, with only ASCII characters.
+		
+		# hash function taken from HT3.
+		# We shift and add : << 4 is a *16
+		"""
+		if len(value) < 1:
+			raise Exception("Size of value must be greater than one")
+		
+		h = 0
+		for letter in value:
+			h = (h << 4) + ord(letter)
+			
+		return h % self._hash_size

02_hash_maps/hm_test.py

@@ -9,6 +9,11 @@ from hm import HMTableCollision
 
 import unittest
 
+class test_hash_map_neighbour_collision(unittest.TestCase):
+
+	def test_add(self):
+		pass
+
 class test_hash_map_table_collision(unittest.TestCase):
 
 	def test_add(self):