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linked_list.py
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linked_list.py
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class DoubleLinkedListNode():
def __init__(self, key=None):
self.prev = None
self.next = None
self.key = key
class DoubleLinkedList():
def __init__(self):
self.nil = DoubleLinkedListNode()
self.nil.next = self.nil
self.nil.prev = self.nil
def insert(self, node):
self.nil.next.prev = node
node.next = self.nil.next
self.nil.next = node
node.prev = self.nil
def search(self, key):
node = self.nil.next
while node.key != key and node.key != self.nil.key:
node = node.next
return node
def delete(self, key):
node = self.search(key)
if node.key != self.nil.key:
node.prev.next = node.next
node.next.prev = node.prev
def __eq__(self, other):
list_repr = []
node = self.nil.next
while node.key != self.nil.key:
list_repr.append(node.key)
node = node.next
return list_repr == other
def __repr__(self):
list_repr = []
node = self.nil.next
while node.key != self.nil.key:
list_repr.append(node.key)
node = node.next
return str(list_repr)
def __add__(self, other):
new_list = DoubleLinkedList()
new_list.nil.next = self.nil.next
new_list.nil.prev = other.nil.prev
self.nil.prev.next = other.nil.next
other.nil.next.prev = self.nil.prev
new_list.nil.next.prev = new_list.nil
new_list.nil.prev.next = new_list.nil
return new_list
# Tests
double_linked_list = DoubleLinkedList()
double_linked_list.insert(DoubleLinkedListNode(1))
double_linked_list.insert(DoubleLinkedListNode(4))
double_linked_list.insert(DoubleLinkedListNode(16))
double_linked_list.insert(DoubleLinkedListNode(9))
assert double_linked_list == [9, 16, 4, 1]
double_linked_list.insert(DoubleLinkedListNode(25))
assert double_linked_list == [25, 9, 16, 4, 1]
double_linked_list.delete(1)
assert double_linked_list == [25, 9, 16, 4]
# Union 10.2.6
double_linked_list2 = DoubleLinkedList()
double_linked_list2.insert(DoubleLinkedListNode(31))
double_linked_list2.insert(DoubleLinkedListNode(98))
double_linked_list2.insert(DoubleLinkedListNode(132))
double_linked_list2.insert(DoubleLinkedListNode(439))
# This destroys original lists, they can't be used anymore.
# It is the price of O(1) operation complexity, because copy of
# lists is as complex as O(n)
new_list = double_linked_list + double_linked_list2
del double_linked_list
del double_linked_list2
assert new_list == [25, 9, 16, 4, 439, 132, 98, 31]
# 10.2-1
class SingleLinkedListNode():
def __init__(self, key=None):
self.next = None
self.key = key
def __eq__(self, other):
return self is other
def __neq__(self, other):
return self is not other
class SingleLinkedList():
def __init__(self):
self.nil = SingleLinkedListNode()
self.nil.next = self.nil
def insert(self, node):
node.next = self.nil.next
self.nil.next = node
def search(self, key):
node = self.nil.next
while node.key != key and node != self.nil:
node = node.next
return node
def search_faster(self, key):
# 10.2-4
node = self.nil.next
self.nil.key = key
while node.key != key:
node = node.next
self.nil.key = None
return node
def search_prev(self, key):
node = self.nil.next
while node.next.key != key and node != self.nil:
node = node.next
return node
def delete(self, key):
node = self.search_prev(key)
if node.next != self.nil:
node.next = node.next.next
def reverse(self):
node = single_linked_list_stack.nil
while True:
node_prev = node
if node_prev.key == single_linked_list_stack.nil.key:
node = node_prev.next
node_next = node_prev.next.next
else:
node = node_next
node_next = node_next.next
node.next = node_prev
if node.key == single_linked_list_stack.nil.key:
break
def __eq__(self, other):
list_repr = []
node = self.nil.next
while node != self.nil:
list_repr.insert(0, node.key)
node = node.next
return list_repr == other
def __repr__(self):
list_repr = []
node = self.nil.next
while node != self.nil:
list_repr.insert(0, node.key)
node = node.next
return str(list_repr)
# Tests
single_linked_list = SingleLinkedList()
single_linked_list.insert(SingleLinkedListNode(1))
single_linked_list.insert(SingleLinkedListNode(4))
single_linked_list.insert(SingleLinkedListNode(16))
single_linked_list.insert(SingleLinkedListNode(9))
assert single_linked_list == [1, 4, 16, 9]
single_linked_list.insert(SingleLinkedListNode(25))
assert single_linked_list == [1, 4, 16, 9, 25]
single_linked_list.delete(1)
assert single_linked_list == [4, 16, 9, 25]
# 10.2-2
class SingleLinkedListStackOverflowError(BaseException):
pass
class SingleLinkedListStackUnderflowError(BaseException):
pass
class SingleLinkedListStack(SingleLinkedList):
top = 0
def stack_empty(self):
return self.top == 0
def push(self, value):
self.insert(SingleLinkedListNode(value))
self.top += 1
def pop(self):
if self.nil.next.key == self.nil.key:
raise SingleLinkedListStackUnderflowError
else:
node = self.nil.next
self.delete(node.key)
self.top -= 1
return node.key
# Tests
single_linked_list_stack = SingleLinkedListStack()
assert single_linked_list_stack.stack_empty()
single_linked_list_stack.push(15)
single_linked_list_stack.push(6)
single_linked_list_stack.push(2)
single_linked_list_stack.push(9)
assert single_linked_list_stack == [15, 6, 2, 9]
assert single_linked_list_stack.top == 4
single_linked_list_stack.push(17)
single_linked_list_stack.push(3)
assert single_linked_list_stack == [15, 6, 2, 9, 17, 3]
assert single_linked_list_stack.top == 6
assert single_linked_list_stack.pop() == 3
assert single_linked_list_stack.top == 5
single_linked_list_stack.push(51)
single_linked_list_stack.pop()
single_linked_list_stack.pop()
single_linked_list_stack.pop()
single_linked_list_stack.pop()
single_linked_list_stack.pop()
single_linked_list_stack.pop()
assert single_linked_list_stack.stack_empty()
try:
single_linked_list_stack.pop()
raise Exception("We can't go there, stack underflow must be raised")
except SingleLinkedListStackUnderflowError:
pass
# 10.2-2
class SingleLinkedListQueueOverflowError(BaseException):
pass
class SingleLinkedListQueueUnderflowError(BaseException):
pass
class SingleLinkedListQueue(SingleLinkedList):
def __init__(self, length):
super(SingleLinkedListQueue, self).__init__()
self.length = length
self.size = 0
self.head = self.nil
self.tail = self.nil
def queue_empty(self):
return self.head == self.tail
def queue_full(self):
return self.size == self.length
def enqueue(self, value):
if self.queue_full():
raise SingleLinkedListQueueOverflowError
else:
node = SingleLinkedListNode(value)
node.next = self.nil
self.tail.next = node
self.tail = node
self.size += 1
def dequeue(self):
if self.queue_empty():
raise SingleLinkedListQueueUnderflowError
else:
value = self.head.next.key
if self.head.next == self.tail:
self.tail = self.head
self.delete(self.head.next.key)
self.size -= 1
return value
single_linked_list_queue = SingleLinkedListQueue(7)
single_linked_list_queue.enqueue(1)
single_linked_list_queue.enqueue(2)
single_linked_list_queue.enqueue(3)
single_linked_list_queue.enqueue(4)
single_linked_list_queue.enqueue(5)
single_linked_list_queue.enqueue(6)
single_linked_list_queue.enqueue(7)
try:
single_linked_list_queue.enqueue(8)
raise Exception("We can't go there, queue overderflow must be raised")
except SingleLinkedListQueueOverflowError:
pass
assert single_linked_list_queue.dequeue() == 1
assert single_linked_list_queue.dequeue() == 2
assert single_linked_list_queue.dequeue() == 3
assert single_linked_list_queue.dequeue() == 4
assert single_linked_list_queue.dequeue() == 5
assert single_linked_list_queue.dequeue() == 6
assert single_linked_list_queue.dequeue() == 7
try:
single_linked_list_queue.dequeue()
raise Exception("We can't go there, queue underderflow must be raised")
except SingleLinkedListQueueUnderflowError:
pass
single_linked_list_queue.enqueue(1)
single_linked_list_queue.enqueue(2)
single_linked_list_queue.enqueue(3)
single_linked_list_queue.enqueue(4)
single_linked_list_queue.enqueue(5)
single_linked_list_queue.enqueue(6)
single_linked_list_queue.enqueue(7)
assert single_linked_list_queue.dequeue() == 1
assert single_linked_list_queue.dequeue() == 2
single_linked_list_queue.enqueue(6)
single_linked_list_queue.enqueue(7)
assert single_linked_list_queue.dequeue() == 3
assert single_linked_list_queue.dequeue() == 4
# 10.2-7
single_linked_list_stack = SingleLinkedListStack()
single_linked_list_stack.push(15)
single_linked_list_stack.push(6)
single_linked_list_stack.push(2)
single_linked_list_stack.push(9)
assert single_linked_list_stack == [15, 6, 2, 9]
single_linked_list_stack.reverse()
assert single_linked_list_stack == [9, 2, 6, 15]