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hash_map_sc.py
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hash_map_sc.py
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# Name: Jennifer Um
# OSU Email: [email protected]
# Course: CS261 - Data Structures
# Assignment: 6 - Hash Map Implementation
# Due Date: 2022-03-11
# Description: Implement a hash map using chaining.
from a6_include import *
def hash_function_1(key: str) -> int:
"""
Sample Hash function #1 to be used with A5 HashMap implementation
DO NOT CHANGE THIS FUNCTION IN ANY WAY
"""
hash = 0
for letter in key:
hash += ord(letter)
return hash
def hash_function_2(key: str) -> int:
"""
Sample Hash function #2 to be used with A5 HashMap implementation
DO NOT CHANGE THIS FUNCTION IN ANY WAY
"""
hash, index = 0, 0
index = 0
for letter in key:
hash += (index + 1) * ord(letter)
index += 1
return hash
class HashMap:
def __init__(self, capacity: int, function) -> None:
"""
Init new HashMap based on DA with SLL for collision resolution
DO NOT CHANGE THIS METHOD IN ANY WAY
"""
self.buckets = DynamicArray()
for _ in range(capacity):
self.buckets.append(LinkedList())
self.capacity = capacity
self.hash_function = function
self.size = 0
def __str__(self) -> str:
"""
Overrides object's string method
Return content of hash map t in human-readable form
DO NOT CHANGE THIS METHOD IN ANY WAY
"""
out = ''
for i in range(self.buckets.length()):
list = self.buckets.get_at_index(i)
out += str(i) + ': ' + str(list) + '\n'
return out
def clear(self) -> None:
"""
Clear the contents of a hashmap without changing the underlying hash table capacity.
:return: None
"""
for i in range(self.buckets.length()):
self.buckets.set_at_index(i, LinkedList())
self.size = 0
def get(self, key: str) -> object:
"""
Return the value associated with a key.
:param key: key to find the value of
:return:
- Value associated with a key.
- If key is not found, return none.
"""
h = self.hash_function(key)
i = h % self.buckets.length()
node_matching_key = self.buckets.get_at_index(i).contains(key)
if node_matching_key is not None:
return node_matching_key.value
return None
def put(self, key: str, value: object) -> None:
"""
Update the key/ value pair in the hash map.
- If key exists, update associated value.
- If key does not exist, add the key/ value pair.
:param key: key of the node to update
:param value: value of the key
:return: none
"""
h = self.hash_function(key)
i = h % self.buckets.length()
node_matching_key = self.buckets.get_at_index(i).contains(key)
if node_matching_key is None:
self.buckets.get_at_index(i).insert(key,value)
self.size += 1
else:
self.buckets.get_at_index(i).remove(key)
self.buckets.get_at_index(i).insert(key,value)
def remove(self, key: str) -> None:
"""
Remove a key and its associated value.
- If a key is not in the hash map, do nothing.
:param key: key of the node to be removed
:return: none
"""
h = self.hash_function(key)
i = h % self.buckets.length()
if self.buckets.get_at_index(i).contains(key):
self.buckets.get_at_index(i).remove(key)
self.size -= 1
def contains_key(self, key: str) -> bool:
"""
Check if a given key in the hash map.
:param key: key to search for
:return:
- True if key is in the hash map
- otherwise, return False
"""
if self.size == 0:
return False
h = self.hash_function(key)
i = h % self.buckets.length()
if self.buckets.get_at_index(i).contains(key):
return True
else:
return False
def empty_buckets(self) -> int:
"""
Get the number of empty buckets in a hash table
:return: the number of empty buckets
"""
empty_buckets_count = 0
for i in range(self.buckets.length()):
if self.buckets.get_at_index(i).length() == 0:
empty_buckets_count += 1
return empty_buckets_count
def table_load(self) -> float:
"""
Get the current hash table load factor.
:return: the current hash table load factor
"""
return self.size / self.capacity
def resize_table(self, new_capacity: int) -> None:
"""
Change the capacity of the internal hash table.
- Key / value pairs must remain the same.
- Keys must be rehashed.
- If new_capacity is less than one, do nothing.
:param new_capacity: new capacity of the hash table
:return: none
"""
if new_capacity < 1:
return
da = self.get_keys()
# create a hash map we can reference
old = HashMap(self.capacity, self.hash_function)
for i in range(self.capacity):
old.buckets.set_at_index(i, self.buckets.get_at_index(i))
# clear bucket and reset capacity, but keep size and hash function
self.clear()
self.capacity = new_capacity
self.buckets = DynamicArray()
for _ in range(new_capacity):
self.buckets.append(LinkedList())
for i in range(da.length()):
key = da.get_at_index(i)
value = old.get(key)
self.put(key, value)
def get_keys(self) -> DynamicArray:
"""
Get a dynamic array of all the keys in the hash map.
- Order does not matter.
:return: a dynamic array of keys
"""
da = DynamicArray()
for i in range(self.capacity):
for node in self.buckets.get_at_index(i):
da.append(node.key)
return da
# BASIC TESTING
if __name__ == "__main__":
# print("\nPDF - empty_buckets example 1")
# print("-----------------------------")
# m = HashMap(100, hash_function_1)
# print(m.empty_buckets(), m.size, m.capacity)
# m.put('key1', 10)
# print(m.empty_buckets(), m.size, m.capacity)
# m.put('key2', 20)
# print(m.empty_buckets(), m.size, m.capacity)
# m.put('key1', 30)
# print(m.empty_buckets(), m.size, m.capacity)
# m.put('key4', 40)
# print(m.empty_buckets(), m.size, m.capacity)
#
# print("\nPDF - empty_buckets example 2")
# print("-----------------------------")
# m = HashMap(50, hash_function_1)
# for i in range(150):
# m.put('key' + str(i), i * 100)
# if i % 30 == 0:
# print(m.empty_buckets(), m.size, m.capacity)
#
# print("\nPDF - table_load example 1")
# print("--------------------------")
# m = HashMap(100, hash_function_1)
# print(m.table_load())
# m.put('key1', 10)
# print(m.table_load())
# m.put('key2', 20)
# print(m.table_load())
# m.put('key1', 30)
# print(m.table_load())
# #
# print("\nPDF - table_load example 2")
# print("--------------------------")
# m = HashMap(50, hash_function_1)
# for i in range(50):
# m.put('key' + str(i), i * 100)
# if i % 10 == 0:
# print(m.table_load(), m.size, m.capacity)
#
# print("\nPDF - clear example 1")
# print("---------------------")
# m = HashMap(100, hash_function_1)
# print("pre", m.size, m.capacity)
# m.put('key1', 10)
# m.put('key2', 20)
# m.put('key1', 30)
# print("postadd",m.size, m.capacity)
# m.clear()
# print(m.size, m.capacity, m)
# print("\nPDF - clear example 2")
# print("---------------------")
# m = HashMap(50, hash_function_1)
# print(m.size, m.capacity)
# m.put('key1', 10)
# print(m.size, m.capacity)
# m.put('key2', 20)
# print(m.size, m.capacity)
# m.resize_table(100)
# print(m.size, m.capacity)
# m.clear()
# print(m.size, m.capacity, m)
#
# print("\nPDF - put example 1")
# print("-------------------")
# m = HashMap(50, hash_function_1)
# for i in range(150):
# m.put('str' + str(i), i * 100)
# if i % 25 == 24:
# print(m.empty_buckets(), m.table_load(), m.size, m.capacity)
#
# print("\nPDF - put example 2")
# print("-------------------")
# m = HashMap(40, hash_function_2)
# for i in range(50):
# m.put('str' + str(i // 3), i * 100)
# if i % 10 == 9:
# print(m.empty_buckets(), m.table_load(), m.size, m.capacity)
#
print("\nPDF - contains_key example 1")
print("----------------------------")
m = HashMap(10, hash_function_1)
print(m.contains_key('key1'))
m.put('key1', 10)
m.put('key2', 20)
m.put('key3', 30)
print(m.contains_key('key1'))
print(m.contains_key('key4'))
print(m.contains_key('key2'))
print(m.contains_key('key3'))
m.remove('key3')
print(m.contains_key('key3'))
#
# print("\nPDF - contains_key example 2")
# print("----------------------------")
# m = HashMap(75, hash_function_2)
# keys = [i for i in range(1, 1000, 20)]
# for key in keys:
# m.put(str(key), key * 42)
# print(m.size, m.capacity)
# result = True
# for key in keys:
# # all inserted keys must be present
# result &= m.contains_key(str(key))
# # NOT inserted keys must be absent
# result &= not m.contains_key(str(key + 1))
# print(result)
#
# print("\nPDF - get example 1")
# print("-------------------")
# m = HashMap(30, hash_function_1)
# print(m.get('key'))
# m.put('key1', 10)
# print(m.get('key1'))
# #
# print("\nPDF - get example 2")
# print("-------------------")
# m = HashMap(150, hash_function_2)
# for i in range(200, 300, 7):
# m.put(str(i), i * 10)
# print(m.size, m.capacity)
# for i in range(200, 300, 21):
# print(i, m.get(str(i)), m.get(str(i)) == i * 10)
# print(i + 1, m.get(str(i + 1)), m.get(str(i + 1)) == (i + 1) * 10)
#
# print("\nPDF - remove example 1")
# print("----------------------")
# m = HashMap(50, hash_function_1)
# print(m.get('key1'))
# m.put('key1', 10)
# print(m.get('key1'))
# m.remove('key1')
# print(m.get('key1'))
# m.remove('key4')
#
# print("\nPDF - resize example 1")
# print("----------------------")
# m = HashMap(20, hash_function_1)
# m.put('key1', 10)
# print(m.size, m.capacity, m.get('key1'), m.contains_key('key1'))
# m.resize_table(30)
# print(m.size, m.capacity, m.get('key1'), m.contains_key('key1'),"\n", m)
# print("\nPDF - resize example 2")
# print("----------------------")
# m = HashMap(75, hash_function_2)
# keys = [i for i in range(1, 1000, 13)]
# for key in keys:
# m.put(str(key), key * 42)
# print(m.size, m.capacity)
#
# for capacity in range(111, 1000, 117):
# m.resize_table(capacity)
#
# m.put('some key', 'some value')
# result = m.contains_key('some key')
# m.remove('some key')
#
# for key in keys:
# result &= m.contains_key(str(key))
# result &= not m.contains_key(str(key + 1))
# print(capacity, result, m.size, m.capacity, round(m.table_load(), 2))
# print("\nPDF - get_keys example 1")
# print("------------------------")
# m = HashMap(10, hash_function_2)
# for i in range(100, 200, 10):
# m.put(str(i), str(i * 10))
# print(m.get_keys())
# print("m.capacity=", m.capacity)
# print(m)
#
# print()
# m.resize_table(1)
# print(m.get_keys())
# print("m.capacity=", m.capacity)
# print(m)
# print()
# m.put('200', '2000')
# m.remove('100')
# m.resize_table(2)
# print(m.get_keys())