algorithms/queue/queue.py at master · ii0/algorithms · GitHub

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# Queue Abstract Data Type (ADT)

# * Queue() creates a new queue that is empty.

# It needs no parameters and returns an empty queue.

# * enqueue(item) adds a new item to the rear of the queue.

# It needs the item and returns nothing.

# * dequeue() removes the front item from the queue.

# It needs no parameters and returns the item. The queue is modified.

# * isEmpty() tests to see whether the queue is empty.

# It needs no parameters and returns a boolean value.

# * size() returns the number of items in the queue.

# It needs no parameters and returns an integer.

class AbstractQueue:

def __init__(self):

self.top = 0

def isEmpty(self):

return self.top == 0

def __len__(self):

return self.top

def __str__(self):

result = '------\n'

for element in self:

result += str(element) + '\n'

return result[:-1] + '\n------'

class ArrayQueue(AbstractStack):

def __init__(self, size=10):

"""

Initialize python List with size of 10 or user given input.

Python List type is a dynamic array, so we have to restrict its

dynamic nature to make it work like a static array.

"""

AbstractStack.__init__(self)

self.array = [None] * size

self.front = 0

self.rear = 0

def enqueue(self, value):

if self.top == len(self.array):

self.expand()

self.array[self.top] = value

self.top += 1

def dequeue(self):

if self.isEmpty():

raise IndexError("stack is empty")

value = self.array[self.top - 1]

self.array[self.top - 1] = None

self.top -= 1

return value

def expand(self):

"""

expands size of the array.

Time Complexity: O(n)

"""

new_array = [None] * len(self.array) * 2 # double the size of the array

for i, element in enumerate(self.array):

new_array[i] = element

self.array = new_array

def __iter__(self):

probe = self.top - 1

while True:

if probe < 0:

raise StopIteration

yield self.array[probe]

probe -= 1

class QueueNode(object):

def __init__(self, value):

self.value = value

self.next = None

class LinkedListQueue(AbstractStack):

def __init__(self):

AbstractQueue.__init__(self)

self.front = None

self.rear = None

def enqueue(self, value):

node = QueueNode(value)

if not front:

self.front = node

self.rear = node

else:

self.rear.next = node

self.rear = node

self.top += 1

def dequeue(self):

if self.isEmpty():

raise IndexError("Queue is empty")

value = self.front.value

if self.front is self.rear:

self.rear = None

self.front = self.front.next

self.top -= 1

return value

def __iter__(self):

probe = self.head

while True:

if probe is None:

raise StopIteration

yield probe.value

probe = probe.next

class HeapPriorityQueue(AbstractStack):

def __init__(self):

pass

algorithms/queue/queue.py at master · ii0/algorithms · GitHub

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