1. class Node(object):
    2.     """单个节点 """
    3.     def __init__(self, elem):
    4.         # 该节点存放的数据
    5.         self.elem = elem
    6.         # 指向下个节点的标识
    7.         self.next = None
    10. class SingleLinkList(object):
    11.     """单循环链表"""
    12.     def __init__(self, node=None):
    13.         self.__head = node
    14.         if node is not None:
    15.             node.next = node
    17.     def is_empty(self):
    18.         """判断是否为空"""
    19.         return self.__head is None
    21.     def length(self):
    22.         """求长度"""
    23.         # cur游标，用来移动遍历节点
    24.         cur = self.__head
    25.         # count记录数量
    26.         count = 1
    27.         if self.is_empty():
    28.             return 0
    29.         else:
    30.             while cur.next != self.__head:
    31.                 count += 1
    32.                 cur = cur.next
    33.             return count
    35.     def travel(self):
    36.         """遍历"""
    37.         cur = self.__head
    38.         if self.is_empty():
    39.             return
    40.         else:
    41.             while cur.next != self.__head:
    42.                 print(cur.elem, end=" ")
    43.                 cur = cur.next
    44.             print(cur.elem)
    45.             print("")
    47.     def add(self, item):
    48.         """头部添加元素，头插法"""
    49.         node = Node(item)
    50.         cur = self.__head
    51.         if self.is_empty():
    52.             self.__head = node
    53.             node.next = self.__head
    54.         else:
    55.             while cur.next != self.__head:
    56.                 cur = cur.next
    57.             cur.next = node
    58.             node.next = self.__head
    59.             self.__head = node
    61.     def append(self, item):
    62.         """尾部添加元素，尾插发"""
    63.         node = Node(item)
    64.         cur = self.__head
    65.         if self.is_empty():
    66.             self.__head = node
    67.             node.next = self.__head
    68.         else:
    69.             while cur.next != self.__head:
    70.                 cur = cur.next
    71.             cur.next = node
    72.             node.next = self.__head
    74.     def insert(self, pos, item):
    75.         """指定位置添加元素
    76.         :param item:节点数据
    77.         :param pos:插入位置，从0开始
    78.         """
    79.         if pos <= 0:
    80.             self.add(item)
    81.         elif pos > (self.length() - 1):
    82.             self.append(item)
    83.         else:
    84.             node = Node(item)
    85.             pre = self.__head
    86.             count = 0
    87.             while count < (pos - 1):
    88.                 pre = pre.next
    89.                 count += 1
    90.             # 当循环退出后，pre指向pos-1位置
    91.             node.next = pre.next
    92.             pre.next = node
    94.     def remove(self, item):
    95.         """删除指定元素"""
    96.         if self.is_empty():
    97.             return False
    98.         pre = None
    99.         cur = self.__head
    100.         while cur.next != self.__head:
    101.             if cur.elem == item:
    102.                 # 此节点是头节点的情况
    103.                 if cur == self.__head:
    104.                     rear = self.__head
    105.                     while rear.next != self.__head:
    106.                         rear = rear.next
    107.                     self.__head = cur.next
    108.                     rear.next = self.__head
    109.                 else:
    110.                     # 中间节点
    111.                     pre.next = cur.next
    112.                 return True
    113.             else:
    114.                 pre = cur
    115.                 cur = cur.next
    116.         # 退出循环，cur指向尾节点
    117.         if cur.elem == item:
    118.             if cur == self.__head:
    119.                 # 只有一个节点
    120.                 self.__head = None
    121.             else:
    122.                 pre.next = cur.next
    123.             return True
    124.         else:
    125.             return False
    127.     def search(self, item):
    128.         """查看节点是否存在"""
    129.         cur = self.__head
    130.         if self.is_empty():
    131.             return  False
    132.         while cur.next != self.__head:
    133.             if cur.elem == item:
    134.                 return True
    135.             else:
    136.                 cur = cur.next
    137.         if cur.elem == item:
    138.             return True
    139.         else:
    140.             return False