class BetterQueue():
"""A stack class implemented as a linked list. Push, pop, peek, and len are all O(1). str is O(n)."""
def __init__(self, initialData=None):
"""Initializer."""
self.head = None
self.size = 0
if initialData != None:
self.push(initialData)
def __len__(self):
"""Returns the length of the queue."""
return self.size
def __str__(self):
"""Returns a string representing the queue, in the same style as a list does."""
returnVal = []
node = self.head
for i in range(self.size):
returnVal.append(node.data)
node = node.next
return str(returnVal)
def push(self, newData):
"""Add data to the end of the stack."""
if self.head == None:
self.head = Link(newData)
else:
self.head.previous.insertAfter(Link(newData))
self.size += 1
def pop(self):
"""Return data from the beginning of the stack."""
data = None
if self.size > 0:
data = self.head.data
self.size -= 1
newHead = self.head.next
self.head.remove()
self.head = newHead
if self.size == 0:
head = None
else:
raise IndexError("Queue is empty.")
return data
def peek(self):
"""Return data from the beginning of the stack without popping it."""
data = None
if self.size > 0:
data = self.head.data
else:
raise IndexError("Queue is empty.")
return data
def clear(self):
"""Clears the queue."""
self.size = 0
self.head = None
class LLObj():
"""Linked list object"""
def __init__(self, data=None):
"""Initializer."""
self.head = LLLink(data)
self.head.next = self.head
self.head.previous = self.head
def findData(self, data):
"""Searches the list for the desired data. Returns the FIRST link which holds it, or None."""
curLink = self.head
returnVal = None
if curLink.data == data:
returnVal = curLink
else:
while curLink.data != data:
curLink = curLink.next
if curLink.data == data:
returnVal = curLink
return returnVal
def insertBefore(self, newData, oldData=None):
"""Insert before the chosen data, or at the front of the list if None is passed,
or append to the end if no matching data. If inserting before the head node, the new node
is set to the head."""
newLink = LLLink(newData)
if oldData == None:
self.head.insertBefore(newLink)
self.head = newLink
else:
desiredLink = self.findData(oldData)
if desiredLink != None:
desiredLink.insertBefore(newLink)
if desiredLink == self.head:
self.head = newLink
else:
self.head.insertBefore(newLink)
def insertAfter(self, newData, oldData=None):
"""Insert after specified data, or at the end of the list if data == None or not present."""
newLink = LLLink(newData)
if oldData == None:
self.head.insertBefore(newLink)
else:
desiredLink = self.findData(oldData)
if desiredLink != None:
desiredLink.insertAfter(newLink)
else:
self.head.insertBefore(newLink)
def getList(self):
"""Returns the LinkedList as a standard Python List."""
curLink = self.head
returnVal = []
returnVal.append(curLink.data)
curLink = curLink.next
while curLink != self.head:
returnVal.append(curLink.data)
curLink = curLink.next
return returnVal
def push(self, newData):
"""Add data to the end of the stack."""
if self.head == None:
self.head = Link(newData)
else:
self.head.previous.insertAfter(Link(newData))
self.size += 1
def insertAfter(self, newData, oldData=None):
"""Insert after specified data, or at the end of the list if data == None or not present."""
newLink = LLLink(newData)
if oldData == None:
self.head.insertBefore(newLink)
else:
desiredLink = self.findData(oldData)
if desiredLink != None:
desiredLink.insertAfter(newLink)
else:
self.head.insertBefore(newLink)
def insertBefore(self, newData, oldData=None):
"""Insert before the chosen data, or at the front of the list if None is passed,
or append to the end if no matching data. If inserting before the head node, the new node
is set to the head."""
newLink = LLLink(newData)
if oldData == None:
self.head.insertBefore(newLink)
self.head = newLink
else:
desiredLink = self.findData(oldData)
if desiredLink != None:
desiredLink.insertBefore(newLink)
if desiredLink == self.head:
self.head = newLink
else:
self.head.insertBefore(newLink)
def __init__(self, data=None):
"""Initializer."""
self.head = LLLink(data)
self.head.next = self.head
self.head.previous = self.head
def test_link(self):
testLink = LLLink("A")
self.assertEqual(testLink.next, testLink)
self.assertEqual(testLink.previous, testLink)
self.assertEqual(testLink.data, "A")