线性: 内存连续,下标结构
链式: 不连续,无下标,append(追加方便)find(遍历)
单链:root ( 入口) --> head(头节点)–>node/next( 节点和指针)–>… tail (尾节点)
linked list data : root ,length
method: init , append, append left, iter_node, remove, find, popleft
代码实现:
class Node(object):
def __init__(self, value=None, next=None):
self.value, self.next = value, next
class LinkedList(object):
def __init__(self, maxsize=None):
self.maxsize = maxsize
self.root = Node()
self.length = 0
self.tailnode = None
def __len__(self):
return self.length
def append(self, value):
if self.maxsize is not None and len(self) > self.maxsize:
return Exception("Full")
node = Node(value)
tailnode = self.tailnode
if tailnode is None: # 第一个插入的值作为root入口的下一个节点。
self.root.next = node
else:
tailnode.next = node # 后面每加一个值就作为尾节点。
self.tailnode = node
self.length += 1
def appendLeft(self, value):
headnode = self.root.next
node = Node(value)
self.root.next = node
node.next = headnode
self.length += 1
def iter_node(self):
# 遍历节点,每次返回当前节点的下一个节点
currnode = self.root.next
while currnode is not self.tailnode:
yield currnode
currnode = currnode.next
yield currnode # 返回最后的尾节点
def __iter__(self): # 需要和上面函数配合完成遍历节点
for node in self.iter_node():
yield node.value
def remove(self, value): # O(n)
prenode = self.root
currnode = self.root.next
while currnode.next is not None:
if currnode.value == value:
prenode.next = currnode.next
del currnode
self.length -= 1
return
def find(self, value): # O(n)
index = 0
for node in self.iter_node():
if node.value == value:
return index
index += 1
return -1
def popleft(self): # O(1)
if self.root.next is None:
raise Exception("pop from empty.")
headnode = self.root.next
self.root.next = headnode.next
self.length -= 1
value = headnode.value
del headnode
return value
def clear(self):
for node in self.iter_node():
del node
self.root.next = None
self.length = 0
def test_linked_list():
ll = LinkedList()
ll.append(0)
ll.append(1)
ll.append(2)
assert len(ll) == 3
assert ll.find(2) == 2
assert ll.find(3) == -1
ll.remove(0)
assert len(ll) == 2
assert ll.find(0) == -1
assert list(ll) == [1, 2]
ll.appendLeft(0)
assert list(ll) == [0, 1, 2]
assert len(ll) == 3
headvalue = ll.popleft()
assert headvalue == 0
assert len(ll) == 2
assert list(ll) == [1, 2]
ll.clear()
assert len(ll) == 0