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linked_list.py
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285 lines (254 loc) · 7.36 KB
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"""
Author: OMKAR PATHAK
Created On: 5th August 2017
Linked l_list and Node can be accommodated
in separate classes for convenience
"""
import inspect
class Node(object):
"""
Node class for creating a node
for linked list.
Each node has its data and a pointer that
points to next node in the Linked l_list
"""
def __init__(self, data, next_node=None):
"""
constructor
:param data:
:param next_node:
"""
self.data = data
self.next = next_node
@staticmethod
def get_code():
"""
return the code for the current class
"""
return inspect.getsource(Node)
class SinglyLinkedList(object):
"""
Defining the head of the linked list
"""
def __init__(self):
"""
constructor
"""
self.head = None
def _search(self, node, data):
"""
searches the node, if valid returns the node else return false
"""
if node is None:
return False
if node.data == data:
return node
return self._search(node.get_next(), data)
def get_data(self):
"""
prints the elements in the linked list
"""
temp = self.head
l_list = []
while temp:
l_list.append(temp.data)
temp = temp.next
return l_list
def insert_at_start(self, data):
"""
insert an item at the beginning of the linked list
"""
if self.head is None:
new_node = Node(data)
self.head = new_node
else:
new_node = Node(data)
new_node.next = self.head
self.head = new_node
def insert_after(self, next_node_data, data):
"""
insert an item after an element in the linked list
"""
new_node = Node(data)
current_node = self._search(self.head, next_node_data)
new_node.next = current_node.next
current_node.next = new_node
def insert_at_end(self, data):
"""
insert an item at the end of the linked list
"""
new_node = Node(data)
temp = self.head
# get last node
while temp.next is not None:
temp = temp.next
temp.next = new_node
def delete(self, data):
"""
to delete specified element from the linked list
"""
temp = self.head
# if data/key is found in head node itself
if temp is not None:
if temp.data == data:
self.head = temp.next
return
else:
# else search all the nodes
while temp.next is not None:
if temp.data == data:
break
# save current node as previous so that we can go on to next node
prev = temp
temp = temp.next
# node not found
if temp is None:
return
# TODO: local variable 'prev' might be referenced before assignment
# TODO: Fix this
prev.next = temp.next
return
@staticmethod
def get_code():
"""
return the code for the current class
"""
return inspect.getsource(SinglyLinkedList)
class DoublyLinkedList(object):
"""DoublyLinkedList
DoublyLinkedList Class
"""
def __init__(self):
"""
constructor
"""
self.head = None
def get_data(self):
"""
prints the elements in the linked list
"""
temp = self.head
l_list = []
while temp:
l_list.append(temp.data)
temp = temp.next
return l_list
def insert_at_start(self, data):
"""
insert an element at the beginning of the linked list
"""
if self.head is None:
self.head = Node(data)
else:
new_node = Node(data)
self.head.previous = new_node
new_node.next = self.head
self.head = new_node
def insert_at_end(self, data):
"""
insert an element at the end of the linked list
"""
new_node = Node(data)
temp = self.head
while temp.next is not None:
temp = temp.next
temp.next = new_node
new_node.previous = temp
def delete(self, data):
"""
to delete specified element from the linked list
"""
temp = self.head
if temp.next is not None:
# if head node is to be deleted
if temp.data == data:
temp.next.previous = None
self.head = temp.next
temp.next = None
return
else:
while temp.next is not None:
if temp.data == data:
break
temp = temp.next
if temp.next:
# if element to be deleted is in between
temp.previous.next = temp.next
temp.next.previous = temp.previous
temp.next = None
temp.previous = None
else:
# if element to be deleted is the last element
temp.previous.next = None
temp.previous = None
return
if temp is None:
return
@staticmethod
def get_code():
"""
returns the code of the current class
"""
return inspect.getsource(DoublyLinkedList)
class CircularLinkedList(object):
'''
Class for circular linked list
'''
def __init__(self):
self.head = None
self.tail = None
self.size = 0
def clear(self):
''' clears the head and tails of the linked list '''
self.tail = None
self.head = None
def get_data(self):
"""
prints the elements in the linked list
"""
l_list = []
current = self.tail
while True:
l_list.append(current.data)
current = current.next
if current == self.tail:
break
return l_list
def insert(self, data):
''' inserts the data in to the linked list '''
node = Node(data)
if self.head:
self.head.next = node
self.head = node
else:
self.head = node
self.tail = node
self.head.next = self.tail
self.size += 1
def delete(self, data):
''' deletes the specified element from linked list '''
current = self.tail
prev = self.tail
while prev == current or prev != self.head:
if current.data == data:
if current == self.tail:
self.tail = current.next
self.head.next = self.tail
else:
prev.next = current.next
self.size -= 1
return
prev = current
current = current.next
@staticmethod
def get_code():
"""
returns the code of the current class
"""
return inspect.getsource(CircularLinkedList)
if __name__ == '__main__':
cll = CircularLinkedList()
cll.insert(1)
cll.insert(2)
cll.insert(3)
print(cll.get_data())