def insert(self, index, value):
if index < 0 or index >= self.size:
return
new_node = Node(None, value)
if index == 0:
new_node.set_next(self.head)
self.head = new_node
self.size += 1
return
current = self.head
while index - 1 is not 0:
current = current.get_next()
index -= 1
current_next = current.get_next()
new_node.set_next(current_next)
current.set_next(new_node)
if new_node.get_next() is None:
self.tail = new_node
self.size += 1
class LinkedList:
def __init__(self):
self.head = None
self.tail = None
self.size = 0
def size(self):
return self.size
def empty(self):
return self.size == 0
def value_at(self, index):
if index < 0 or index >= self.size:
return None
current = self.head
while index is not 0:
current = current.get_next()
index -= 1
return current.get_value()
def push_front(self, value):
self.head = Node(self.head, value)
self.size += 1
def pop_front(self):
if self.empty():
return None
value = self.head.get_value()
self.head = self.head.get_next()
if self.head is None:
self.tail = None
self.size -= 1
return value
def push_back(self, value):
node_ = Node(None, value)
if self.empty():
self.head = node_
self.tail = node_
else:
self.tail.set_next(node_)
self.tail = node_
self.size += 1
def pop_back(self):
if self.empty():
return None
current = self.head
while current.get_next() is not None:
next_ = current.get_next()
if next_ == self.tail:
value = next_.get_value()
current.set_next(None)
self.tail = current
self.size -= 1
return value
current = current.get_next()
return self.pop_front()
def front(self):
return self.head.get_value()
def back(self):
return self.tail.get_value()
def insert(self, index, value):
if index < 0 or index >= self.size:
return
new_node = Node(None, value)
if index == 0:
new_node.set_next(self.head)
self.head = new_node
self.size += 1
return
current = self.head
while index - 1 is not 0:
current = current.get_next()
index -= 1
current_next = current.get_next()
new_node.set_next(current_next)
current.set_next(new_node)
if new_node.get_next() is None:
self.tail = new_node
self.size += 1
def erase(self, index):
if index < 0 or index >= self.size:
return
if index == 0:
self.pop_front()
return
if index == self.size - 1:
self.pop_back()
return
current = self.head
while index - 1 is not 0:
index -= 1
current = current.get_next()
current.set_next(current.get_next().get_next())
self.size -= 1
if current.get_next() is None:
self.tail = current
def value_n_from_end(self, n):
if n < 0 or n >= self.size:
return None
if n == 0:
return self.tail.get_value()
elif n == self.size - 1:
return self.head.get_value()
current = self.head
while n is not 0:
current = current.get_next()
n -= 1
return current.get_value()
def remove_value(self, value):
if self.head.get_value() == value:
self.pop_front()
elif self.tail.get_value() == value:
self.pop_back()
else:
current = self.head
while current.get_next() is not None:
if current.get_value() == value:
current.set_next(current.get_next().get_next())
if current.get_next() is None:
self.tail = current
def reverse(self):
if self.empty():
return
prev = None
current = self.head
self.tail = current
while current is not None:
next_ = current.get_next()
current.set_next(prev)
prev = current
current = next_
self.head = prev