1 # -*- coding: utf-8 -*-
  2 # @author: Tele
  3 # @Time  : 2019/04/22 下午 3:17
  4 # 单向链表的实现
  5 # 每个节点包含两部分,数据区和指向下个节点的链接
  6 # 单向列表:每个节点包含两部分:数据区与链接区(指向下一个节点),最后一个元素的链接区为None
  7 # 单向列表只要找到头节点,就可以访问全部节点
  8 class SingleNode:
  9     def __init__(self, data, next=None):
 10         self.data = data
 11         # next指向下一个节点而不是数据
 12         self.next = next
 13
 14
 15 # 使用链表时只需要传入待存储的数据而不是节点
 16 class SingleLinkedList:
 17     def __init__(self, data=None):
 18         node = SingleNode(data)
 19         self.__head = node if node.data else None
 20
 21     def is_empty(self):
 22         return self.__head == None
 23
 24     def length(self):
 25         count = 0
 26         cur = self.__head
 27         while cur:
 28             count += 1
 29             cur = cur.next
 30         return count
 31
 32     # 头部添加元素
 33     def add(self, data):
 34         node = SingleNode(data)
 35         node.next = self.__head
 36         self.__head = node
 37
 38     # 尾部添加元素
 39     def append(self, data):
 40         node = SingleNode(data)
 41         if self.is_empty():
 42             self.__head = node
 43         else:
 44             cur = self.__head
 45             # 最后一个节点的next为None
 46             while cur.next:
 47                 cur = cur.next
 48             cur.next = node
 49
 50     # 指定位置插入
 51     def insert(self, pos, data):
 52         node = SingleNode(data)
 53         cur = self.__head
 54         count = 0
 55         if self.length() >= pos >= 0:
 56             while cur:
 57                 if count + 1 == pos:
 58                     node.next = cur.next
 59                     cur.next = node
 60                     break
 61                 # pos为0
 62                 elif count == pos:
 63                     self.add(data)
 64                     break
 65                 count += 1
 66                 cur = cur.next
 67         elif pos < 0:
 68             self.add(data)
 69         else:
 70             self.append(data)
 71         # 如果列表中插入时没有元素
 72         if not self.__head:
 73             self.append(data)
 74
 75     # 遍历
 76     def travel(self):
 77         cur = self.__head
 78         while cur:
 79             print(cur.data)
 80             cur = cur.next
 81
 82     # 移除出现的第一个元素
 83     def remove(self, data):
 84         if self.is_empty():
 85             return
 86         node = self.__find(data)
 87         cur = self.__head
 88         while cur:
 89             # 如果要移除的元素是头节点
 90             if cur.data == node.data:
 91                 self.__head = cur.next
 92                 break
 93             elif cur.next.data == node.data:
 94                 cur.next = node.next
 95                 break
 96             cur = cur.next
 97
 98     # 私有方法,用于查找节点
 99     def __find(self, data):
100         cur = self.__head
101         node = SingleNode(data)
102         while cur:
103             if cur.data == data:
104                 node.next = cur.next
105                 break
106             cur = cur.next
107         return node
108
109     # 查找,找不到返回-1,找到则返回索引
110     def search(self, data):
111         index = -1
112         cur = self.__head
113         count = 0
114         while cur:
115             if cur.data == data:
116                 index = count
117                 break
118             count += 1
119             cur = cur.next
120         return index
121
122
123 def main():
124     ssl = SingleLinkedList()
125     print(ssl.is_empty())
126     print(ssl.length())
127     # ssl.append(1)
128     # ssl.append(100)
129     # ssl.append(2)
130     # ssl.append(200)
131     # ssl.append(3)
132     # ssl.append(4)
133     print(ssl.is_empty())
134     print(ssl.length())
135
136     # 遍历
137     print("*" * 50)
138     # ssl.travel()
139
140     ssl.add(100)
141     # ssl.travel()
142     # 为负数时作为头节点
143     ssl.insert(-1, "sss")
144     ssl.travel()
145     print("*" * 50)
146     print(ssl.search("sss"))  # 0
147     print("*" * 50)
148     ssl.remove(100)
149     ssl.travel()
150
151
152 if __name__ == '__main__':
153     main()