class Deque:
def __init__(self, items=None):
"""
initializes a Deque with items if any are given.
If items are given they are populated into Deque with
push_front method (loading in front by default)
"""
# initialize linked list for our deque to use
self.list = DoublyLinkedList()
# build are deque
if items is not None:
for item in items:
self.push_front(item)
def push_front(item):
"""
Takes in given item and prepends it
to the front of the deque
"""
# use linked list prepend method
self.list.prepend(item)
def push_back(item):
"""
Takes an item as parameter and appends it
to the back of the deque
"""
# uses linked list append method
self.list.append(item)
def pop_front():
"""
Removes the item at front of deque
and returns it
"""
# grab item to be popped/returned
popped_item = self.list.head
# remove from left side of list using linkedlist delete method
# note: this is still constant b/c popped_item is first item in linkedlist
self.list.delete(popped_item)
return popped_item # returning item that was just deleted
def pop_back():
"""
Removes the item at the end of deque
and returns its value
"""
# grab item to be removed (tail of linked list)
popped_item = self.list.tail
# remove item from right side
# currently O(n)
self.list.delete(popped_item)
return popped_item # return value of deleted item
def test_length_after_delete(self):
dll = DoublyLinkedList(['A', 'B', 'C', 'D', 'E'])
assert dll.length() == 5
# Delete should decrease length
dll.delete('A')
assert dll.length() == 4
dll.delete('E')
assert dll.length() == 3
dll.delete('C')
assert dll.length() == 2
dll.delete('D')
assert dll.length() == 1
dll.delete('B')
assert dll.length() == 0
def test_delete(self):
dll = DoublyLinkedList()
dll.append('L')
dll.append('K')
dll.append('G')
dll.delete('L')
assert dll.head.data == 'K'
assert dll.tail.data == 'G'
assert dll.length() == 2
print(dll)
dll.delete('K')
assert dll.head.data == 'G'
assert dll.tail.data == 'G'
assert dll.length() == 1
class LinkedQueue(object):
def __init__(self, iterable=None):
"""Initialize this queue and enqueue the given items, if any"""
# Initialize a new linked list to store the items
self.list = DoublyLinkedList()
if iterable:
for item in iterable:
self.enqueue(item)
def __repr__(self):
"""Return a string representation of this queue"""
return 'Queue({} items, front={})'.format(self.length(), self.front())
def is_empty(self):
"""Return True if this queue is empty, or False otherwise"""
# TODO: Check if empty
return self.list.size is 0
def length(self):
"""Return the number of items in this queue"""
# TODO: Count number of items
return self.list.size
def enqueue(self, item):
"""Insert the given item at the back of this queue"""
# TODO: Insert given item
self.list.append(item)
def front(self):
"""Return the item at the front of this queue without removing it,
or None if this queue is empty"""
# TODO: Return front item, if any
if self.is_empty():
return None
return self.list.head.data
def dequeue(self):
"""Remove and return the item at the front of this queue,
or raise ValueError if this queue is empty"""
# TODO: Remove and return front item, if any
if self.is_empty():
raise ValueError('Queue is empty')
item = self.list.head.data
self.list.delete(item)
return item
def test_delete_with_5_items(self):
dll = DoublyLinkedList(['A', 'B', 'C', 'D', 'E'])
assert dll.head.data == 'A' # First item
assert dll.tail.data == 'E' # Last item
dll.delete('A')
assert dll.head.data == 'B' # New head
assert dll.tail.data == 'E' # Unchanged
dll.delete('E')
assert dll.head.data == 'B' # Unchanged
assert dll.tail.data == 'D' # New tail
dll.delete('C')
assert dll.head.data == 'B' # Unchanged
assert dll.tail.data == 'D' # Unchanged
dll.delete('D')
assert dll.head.data == 'B' # Unchanged
assert dll.tail.data == 'B' # New tail
dll.delete('B')
assert dll.head is None # No head
assert dll.tail is None # No tail
def test_delete(self):
ll = DoublyLinkedList(['A', 'B', 'C'])
ll.delete('A')
assert ll.head.data == 'B' # new head
assert ll.tail.data == 'C' # unchanged
assert ll.size == 2
ll.delete('C')
assert ll.head.data == 'B' # unchanged
assert ll.tail.data == 'B' # new tail
assert ll.size == 1
ll.delete('B')
assert ll.head is None # new head
assert ll.tail is None # new head
assert ll.size == 0
with self.assertRaises(ValueError):
ll.delete('X') # item not in list
def test_delete(self):
ll = DoublyLinkedList()
ll.append('A')
ll.append('B')
ll.append('C')
ll.delete('A')
assert ll.head.data == 'B'
assert ll.tail.data == 'C'
ll.delete('C')
assert ll.head.data == 'B'
assert ll.tail.data == 'B'
ll.delete('B')
assert ll.head is None
assert ll.tail is None
with self.assertRaises(ValueError):
ll.delete('D')
def test_delete(self):
dll = DoublyLinkedList()
dll.append('A')
dll.append('B')
dll.append('C')
dll.delete('A')
assert dll.head.data == 'B'
assert dll.tail.data == 'C'
assert dll.size == 2
dll.delete('C')
assert dll.head.data == 'B'
assert dll.tail.data == 'B'
assert dll.size == 1
dll.delete('B')
assert dll.head is None
assert dll.tail is None
assert dll.size == 0
with self.assertRaises(ValueError):
dll.delete('D')
def DISABLE_test_delete(self):
ll = DoublyLinkedList()
ll.append('A')
ll.append('B')
ll.append('C')
ll.delete('A')
assert ll.head.data == 'B'
assert ll.tail.data == 'C'
assert ll.size == 2
ll.delete('C')
assert ll.head.data == 'B'
assert ll.tail.data == 'B'
assert ll.size == 1
ll.delete('B')
assert ll.head is None
assert ll.tail is None
assert ll.size == 0
with self.assertRaises(ValueError):
ll.delete('D')
def test_size(self):
ll = DoublyLinkedList()
assert ll.size == 0
# append and prepend operations increment size
ll.append('B')
assert ll.size == 1
ll.prepend('A')
assert ll.size == 2
ll.append('C')
assert ll.size == 3
# delete operations decrement size
ll.delete('B')
assert ll.size == 2
ll.delete('C')
assert ll.size == 1
ll.delete('A')
assert ll.size == 0
def test_length(self):
ll = DoublyLinkedList()
assert ll.length() == 0
# append and prepend operations increase length
ll.append('B')
assert ll.length() == 1
ll.prepend('A')
assert ll.length() == 2
ll.append('C')
assert ll.length() == 3
# delete operations decrease length
ll.delete('B')
assert ll.length() == 2
ll.delete('C')
assert ll.length() == 1
ll.delete('A')
assert ll.length() == 0
dll.insert(1) assert dll.search(1) == True dll.insert(2) dll.insert(3) assert dll.head.next.data == 2 assert dll.search(3) == True assert dll.search(4) == False print "Test 3 Passed" # Test 4 dll = DoublyLinkedList() assert dll.size() == 0 dll.insert(1) dll.insert(2) dll.insert(3) dll.delete(2) assert dll.tail.prev.data == 3 assert dll.search(2) == False assert dll.search(3) == True assert dll.size() == 2 print "Test 4 Passed" # Test 5 dll = DoublyLinkedList() dll.insert(1) dll.insert(2) dll.insert(3) dll.insert(4) dll.print_list_forward() # Test 6
def test_delete_with_item_not_in_list(self):
dll = DoublyLinkedList(['A', 'B', 'C'])
# Delete should raise error if item not found
with self.assertRaises(ValueError):
dll.delete('X') # Item not found in list
def test_delete_with_3_items(self):
dll = DoublyLinkedList(['A', 'B', 'C'])
assert dll.head.data == 'A' # First item
assert dll.tail.data == 'C' # Last item
dll.delete('A')
assert dll.head.data == 'B' # New head
assert dll.tail.data == 'C' # Unchanged
dll.delete('C')
assert dll.head.data == 'B' # Unchanged
assert dll.tail.data == 'B' # New tail
dll.delete('B')
assert dll.head is None # No head
assert dll.tail is None # No tail
# Delete should raise error if item was already deleted
with self.assertRaises(ValueError):
dll.delete('A') # Item no longer in list
with self.assertRaises(ValueError):
dll.delete('B') # Item no longer in list
with self.assertRaises(ValueError):
dll.delete('C') # Item no longer in list
