Implementation of Hash Table in Python using Separate Chaining
class Node:
def __init__(self, key, value):
self.key = key
self.value = value
self.next = None
class HashTable:
def __init__(self, capacity):
self.capacity = capacity
self.size = 0
self.table = [None] * capacity
def _hash(self, key):
return hash(key) % self.capacity
def insert(self, key, value):
index = self._hash(key)
if self.table[index] is None:
self.table[index] = Node(key, value)
self.size += 1
else:
current = self.table[index]
while current:
if current.key == key:
current.value = value
return
current = current.next
new_node = Node(key, value)
new_node.next = self.table[index]
self.table[index] = new_node
self.size += 1
def search(self, key):
index = self._hash(key)
current = self.table[index]
while current:
if current.key == key:
return current.value
current = current.next
raise KeyError(key)
def remove(self, key):
index = self._hash(key)
previous = None
current = self.table[index]
while current:
if current.key == key:
if previous:
previous.next = current.next
else:
self.table[index] = current.next
self.size -= 1
return
previous = current
current = current.next
raise KeyError(key)
def __len__(self):
return self.size
def __contains__(self, key):
try:
self.search(key)
return True
except KeyError:
return False
if __name__ == '__main__':
ht = HashTable(5)
ht.insert("apple", 3)
ht.insert("banana", 2)
ht.insert("cherry", 5)
print("apple" in ht)
print("durian" in ht)
print(ht.search("banana"))
ht.insert("banana", 4)
print(ht.search("banana"))
ht.remove("apple")
print(len(ht))
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