def __init__(self, iterable=None):
"""Initialize this deque and push_back the given items, if any."""
# Initialize a new linked list to store the items
self.list = LinkedList()
if iterable is not None:
for item in iterable:
self.push_back(item)
def test_delete(self):
ll = LinkedList(['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_replace(self):
ll = LinkedList(['A', 'B', 'C'])
ll.replace('A', 'D')
assert ll.head.data == 'D' # new head
assert ll.tail.data == 'C' # unchanged
assert ll.size == 3
ll.replace('B', 'E')
assert ll.head.data == 'D' # unchanged
assert ll.tail.data == 'C' # unchanged
assert ll.size == 3
ll.replace('C', 'F')
assert ll.head.data == 'D' # unchanged
assert ll.tail.data == 'F' # new tail
assert ll.size == 3
with self.assertRaises(ValueError):
ll.replace('X', 'Y') # item not in list
def test_get_at_index(self):
ll = LinkedList(['A', 'B', 'C'])
assert ll.get_at_index(0) == 'A' # head item
assert ll.get_at_index(1) == 'B' # middle item
assert ll.get_at_index(2) == 'C' # tail item
with self.assertRaises(ValueError):
ll.get_at_index(3) # index too high
with self.assertRaises(ValueError):
ll.get_at_index(-1) # index too low
def test_prepend(self):
ll = LinkedList()
ll.prepend('C')
assert ll.head.data == 'C' # new head
assert ll.tail.data == 'C' # new head
assert ll.size == 1
ll.prepend('B')
assert ll.head.data == 'B' # new head
assert ll.tail.data == 'C' # unchanged
assert ll.size == 2
ll.prepend('A')
assert ll.head.data == 'A' # new head
assert ll.tail.data == 'C' # unchanged
assert ll.size == 3
def test_size(self):
ll = LinkedList()
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 = LinkedList()
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
def test_items(self):
ll = LinkedList()
assert ll.items() == []
ll.append('B')
assert ll.items() == ['B']
ll.prepend('A')
assert ll.items() == ['A', 'B']
ll.append('C')
assert ll.items() == ['A', 'B', 'C']
def test_init_with_list(self):
ll = LinkedList(['A', 'B', 'C'])
assert ll.head.data == 'A' # first item
assert ll.tail.data == 'C' # last item
assert ll.size == 3
def test_init(self):
ll = LinkedList()
assert ll.head is None
assert ll.tail is None
assert ll.size == 0
def test_insert_at_index(self):
ll = LinkedList()
ll.insert_at_index(0, 'B') # append('B')
assert ll.head.data == 'B' # new head (at index 0)
assert ll.tail.data == 'B' # new tail (at index 0)
assert ll.size == 1
ll.insert_at_index(0, 'A') # prepend('A')
assert ll.head.data == 'A' # new head (at index 0)
assert ll.tail.data == 'B' # unchanged (now at index 1)
assert ll.size == 2
ll.insert_at_index(2, 'D') # append('D')
assert ll.head.data == 'A' # unchanged (at index 0)
assert ll.tail.data == 'D' # new tail (now at index 2)
assert ll.size == 3
ll.insert_at_index(2, 'C') # insert 'C' between 'B' and 'D'
assert ll.head.data == 'A' # unchanged (at index 0)
assert ll.tail.data == 'D' # unchanged (now at index 3)
assert ll.tail.previous.data == 'C'
assert ll.head.next.data == 'B'
assert ll.head.next.next.next.data == 'D'
assert ll.tail.previous.previous.next.data == 'C'
assert ll.size == 4
with self.assertRaises(ValueError):
ll.insert_at_index(5, 'X') # index too high
with self.assertRaises(ValueError):
ll.insert_at_index(-1, 'Y') # index too low
def test_find(self):
ll = LinkedList(['A', 'B', 'C'])
assert ll.find(lambda item: item == 'B') == 'B'
assert ll.find(lambda item: item < 'B') == 'A'
assert ll.find(lambda item: item > 'B') == 'C'
assert ll.find(lambda item: item == 'X') is None
class LinkedDeque(object):
# Setting our front as the head of the doubly linked list
def __init__(self, iterable=None):
"""Initialize this deque and push_back the given items, if any."""
# Initialize a new linked list to store the items
self.list = LinkedList()
if iterable is not None:
for item in iterable:
self.push_back(item)
def __repr__(self):
"""Return a string representation of this deque."""
return 'Queue({} items, front={})'.format(self.length(), self.front())
def is_empty(self):
"""Return True if this deque is empty, or False otherwise."""
return self.list.is_empty()
def length(self):
"""Return the number of items in this deque."""
return self.list.length()
def push_front(self, item):
"""Insert the given item at the front of the linkedlist.
Running time: O(1) calling the ll prepend method by just changing the head node"""
self.list.prepend(item)
def push_back(self, item):
"""Insert the given item at the back of this deque.
Running time: O(1) calling the ll append method by just changing the tail node"""
self.list.append(item)
def front(self):
"""Return the item at the front of this deque without removing it,
or None if this deque is empty."""
if self.length() != 0:
return self.list.head.data # returning the head
else:
return None
def back(self):
"""Return the item at the end of this deque without removing it,
or None if this deque is empty."""
if self.length() != 0:
return self.list.tail.data # returning the tail
else:
return None
def pop_front(self):
"""Remove and return the item at the front of this deque,
or raise ValueError if this deque is empty.
Running time: O(1) from getting the front item and removing at the head of the ll"""
if self.length() != 0:
front_item = self.front()
self.list.delete(front_item)
return front_item
else:
raise ValueError('No items in list to pop_front: []')
def pop_back(self):
"""Remove and return the item at the back of this deque,
or raise ValueError if this deque is empty.
Running time: O(1) from getting the back item and removing at the tail of the ll"""
if self.length() != 0:
back_item = self.back()
self.list.delete(back_item)
return back_item
else:
raise ValueError('No items in list to pop_back: []')