数据结构 单链表反转 回顾练习

  1 #!/usr/bin/env python3
  2 
  3 class LNode(object):
  4         def __init__(self, elem, next_=None):
  5                 self.elem = elem
  6                 self.next = next_
  7 
  8 class ListError(Exception):
  9         pass
 10 
 11 class LList(object):
 12         def __init__(self):
 13                 self.head = None
 14                 self.rear = None
 15                 self.num = 0
 16 
 17         def is_empty(self):
 18                 return self.head is None
 19 
 20         def count(self):
 21                 return self.num
 22 
 23         def prepend(self, elem):
 24                 if self.head is None:
 25                         self.head = LNode(elem)
 26                         self.rear = self.head
 27                         self.num += 1
 28                 else:
 29                         self.head = LNode(elem, self.head)
 30                         self.num += 1
 31 
 32         def pop(self):
 33                 if self.head is None:
 34                         raise ListError
 35                 e = self.head.elem
 36                 if self.head.next is None:
 37                         self.rear = None
 38                         self.head = None
 39                         self.num -= 1
 40                         return e
 41                 self.head = self.head.next
 42                 self.num -= 1
 43                 return e
 44 
 45         def append(self, elem):
 46                 if self.head is None:
 47                         self.head = LNode(elem)
 48                         self.rear = self.head
 49                         self.num += 1
 50                         return
 51                 self.rear.next = LNode(elem)
 52                 self.rear = self.rear.next
 53                 self.num += 1
 54 
 55         def pop_last(self):
 56                 if self.head is None:
 57                         raise ListError
 58                 p = self.head
 59                 if p.next is None:
 60                         e = p.elem
 61                         self.head = None
 62                         self.rear = None
 63                         self.num -= 1
 64                         return e
 65                 while p.next.next:
 66                         p = p.next
 67                 e = p.next.elem
 68                 p.next = None
 69                 self.rear = p
 70                 self.num -= 1
 71                 return e
 72 
 73         def bianli(self):
 74                 p = self.head
 75                 li = []
 76                 while p:
 77                         li.append(p.elem)
 78                         p = p.next
 79                 return li
 80 
 81         def reverse(self):
 82                 li = self.bianli()
 83                 li.sort(reverse=True)
 84                 p = self.head
 85                 for i in li:
 86                         p.elem = i
 87                         p = p.next
 88 
 89 if __name__ == ‘__main__‘:
 90         l = LList()
 91         l.append(1)
 92         l.prepend(2)
 93         l.pop()
 94         l.pop_last()
 95         l.append(2)
 96         l.prepend(1)
 97         l.append(3)
 98         print(l.bianli())
 99         l.reverse()
100         print(l.bianli())