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
# assert(ll) == DoublyLinkedList(['A', 'B', 'C'])
assert(ll.head.data) == 'A'
assert(ll.head.prev) == None
assert(ll.head.next.prev.data) == 'A'
assert(ll.tail.data) == 'C'
assert(ll.tail.prev.data) == 'B'
assert(ll.tail.next) == None
ll.delete('B')
assert ll.length() == 2
ll.delete('C')
assert ll.length() == 1
ll.delete('A')
assert ll.length() == 0
class LinkedDeque(object):
'''double-ended queue'''
def __init__(self, iterable=None):
"""Initialize this queue and enqueue the given items, if any."""
self.list = DoublyLinkedList()
self.size = 0
if iterable is not None:
for item in iterable:
self.push_back(item)
def __repr__(self):
"""Return a string representation of this deque."""
return 'Deque({} items, front={})'.format(self.length(), self.front())
def is_empty(self):
"""Return True if this queue is empty, or False otherwise."""
# runtime O(1) checking the value
if self.size == 0:
return True
else:
return False
def length(self):
"""Return the number of items in the deque"""
# runtime O(1) retrieving a variable
return self.size
def push_front(self, item):
"""Insert item at front of deque"""
# runtime O(n) having to shift all the slots in the array back
self.list.prepend(item)
self.size += 1
def push_back(self, item):
"""Insert item at back of the deque"""
# runtime O(1)*average
self.list.append(item)
self.size += 1
def front(self):
"""Returns item at front of deque"""
# runtime O(1) retrieving value at an index
return self.list.head.data
def back(self):
"""Returns item at back of the deque"""
# runtime O(1) retrieving value at an index
return self.list.tail.data
def pop_front(self):
"""Remove and return the item at the front of the deque"""
# runtime O(n) having to shift later elements up the list
self.size -= 1
return self.list.delete_index(0)
def pop_back(self):
"""Remove and return the item at the back of the deque"""
# runtime O(1) removing last element doesnt have effect on other elements
self.size -= 1
return self.list.delete_index(self.size)
def test_items(self):
dll = DoublyLinkedList()
assert dll.items() == []
dll.append('B')
assert dll.items() == ['B']
dll.prepend('A')
assert dll.items() == ['A', 'B']
dll.append('C')
assert dll.items() == ['A', 'B', 'C']
def test_size(self):
dll = DoublyLinkedList()
assert dll.size == 0
# append and prepend operations increment size
dll.append('B')
assert dll.size == 1
dll.prepend('A')
assert dll.size == 2
dll.append('C')
assert dll.size == 3
# delete operations decrement size
dll.delete('B')
assert dll.size == 2
dll.delete('C')
assert dll.size == 1
dll.delete('A')
assert dll.size == 0
def test_length(self):
dll = DoublyLinkedList()
assert dll.length() == 0
# append and prepend operations increase length
dll.append('B')
assert dll.length() == 1
dll.prepend('A')
assert dll.length() == 2
dll.append('C')
assert dll.length() == 3
# delete operations decrease length
dll.delete('B')
assert dll.length() == 2
dll.delete('C')
assert dll.length() == 1
dll.delete('A')
assert dll.length() == 0
def test_append(self):
dll = DoublyLinkedList()
dll.append('A')
assert dll.head.data == 'A' # new head
assert dll.tail.data == 'A' # new tail
assert dll.size == 1
dll.append('B')
assert dll.head.data == 'A' # unchanged
assert dll.tail.data == 'B' # new tail
# checking to see if pointers have the same memory address
assert dll.head.next is dll.tail
assert dll.head is dll.tail.previous
assert dll.head.previous == None
assert dll.tail.next == None
assert dll.size == 2
dll.append('C')
assert dll.head.data == 'A' # unchanged
assert dll.tail.data == 'C' # new tail
assert dll.head.next.next is dll.tail # two links right
assert dll.head.next is dll.tail.previous # one link right, one link left
assert dll.head is dll.tail.previous.previous # two links left
assert dll.head.previous == None
assert dll.tail.next == None
assert dll.size == 3
def test_append(self):
ll = DoublyLinkedList()
ll.append('A')
assert ll.head.data == 'A' # new head
assert ll.tail.data == 'A' # new tail
assert ll.size == 1
ll.append('B')
assert ll.head.data == 'A' # unchanged
assert ll.tail.data == 'B' # new tail
assert ll.size == 2
ll.append('C')
assert ll.head.data == 'A' # unchanged
assert ll.tail.data == 'C' # new tail
assert ll.size == 3