single linked list（單鏈表）
主要的操作是iter（遍歷）、insert（插入）、find（查找）和delete（刪除）。
以上操作的時間複雜度都是O(N)。
#! /usr/bin/env python3
# coding:utf-8
class SingleLinkedListError(Exception): pass
class SingleLinkedListOperationError(SingleLinkedListError): pass
class Node:
def __init__(self, data, next=None):
self.data = data
self.next = next
class SingleLinkedList:
def __init__(self):
self.head = None
def is_empty(self):
return self.head == None
def insert(self, node):
if self.is_empty():
self.head = node
self.head.next = None
else:
node.next = self.head
self.head = node
def iter(self):
current_node = self.head
while current_node != None:
yield current_node
current_node = current_node.next
def find(self, value):
for node in self.iter():
if node.data == value:
return node
return None
def find_before(self, target):
for node in self.iter():
if node.next == target:
return node
return None
def delete(self, value):
# case 1 : empty list
if self.is_empty():
raise SingleLinkedListOperationError("delete call in"
" a empty list")
target = self.find(value)
if target != None:
# case 2 : singleton list
if self.head == target:
self.head = self.head.next
# case 3 : multi node list
else:
before = self.find_before(target)
before.next = target.next
del target # don't forget this