编程练习 输入一个链表 从尾到头打印节点值

Posted 2020-09-01 小黄人python

两种方法

1，利用栈的方法实现

将节点里的值按顺序push压入到栈中

再将pop出栈的值按顺序赋值到节点里

 

2.原链表头节点删除 再 头插入到一个新的链表里 实现反转

 

  1 #!/usr/bin/env python3
  2 
  3 class Stack(object):
  4         def __init__(self):
  5                 self._elems = []
  6 
  7         def is_empty(self):
  8                 return self._elems == []
  9 
 10         def push(self, elem):
 11                 self._elems.append(elem)
 12 
 13         def pop(self):
 14                 if self.is_empty():
 15                         raise ValueError("Stack is Empty")
 16                 return self._elems.pop()
 17 
 18         def peek(self):
 19                 if self.is_empty():
 20                         raise ValueError("Stack is Empty")
 21                 return self._elems[-1]
 22 
 23         def bianli(self):
 24                 return self._elems
 25 
 26 class Node(object):
 27         def __init__(self, elem, next_=None):
 28                 self.elem = elem
 29                 self.next = next_
 30 
 31 class Simple_List(object):
 32         def __init__(self):
 33                 self.head = None
 34                 self.rear = None
 35 
 36         def is_empty(self):
 37                 return self.head is None
 38 
 39         def prepend(self, elem):
　　　　               if self.head is None: 
 40                         self.head = Node(elem)
 41                         self.rear = self.head
 42                 else:
 43                         self.head = Node(elem, self.head)
 44 
 45         def prepop(self):
 46                 if self.head is None:
 47                         raise ValueError("List is Empty")
 48                 e = self.head.elem
 49                 self.head = self.head.next
 50                 return e
 51 
 52         def append(self, elem):
 53                 if self.head is None:
 54                         self.head = Node(elem)
 55                         self.rear = self.head
 56                 else:
 57                         self.rear = Node(elem)
 58                         self.rear = self.rear.next
 59 
 60         def pop(self):
 61                 if self.head is None:
 62                         raise ValueError("List is Empty")
 63                 p = self.head
 64                 if p.next is None:
 65                         self.head = None
 66                 while p.next.next:
 67                         p = p.next
 68                 e = p.next.elem
 69                 p.next = None
 70                 self.rear = p
 71                 return e
 72 
 73         def reverse_stack(self):
 74                 s1 = Stack()
 75                 p = self.head
 76                 while p:
 77                         s1.push(p.elem)
 78                         p = p.next
 79                 p = self.head
 80                 while p:
 81                         p.elem = s1.pop()
 82                         p = p.next
 83 
 84         def reverse(self):
 85                 li = Simple_List()
 86                 while not self.is_empty():
 87                         li.prepend(self.prepop())
 88                 return li
 89 
 90         def bianli(self):
 91                 p = self.head
 92                 li = []
 93                 while p:
 94                         li.append(p.elem)
 95                         p = p.next
 96                 return li
 97 
 98 if __name__==‘__main__‘:
 99         l = Simple_List()
100         for i in range(10):
101                 l.prepend(i)
102         print("origin list:",l.bianli())
103         l.reverse_stack()
104         print("stack reverse:",l.bianli())
105         print("prepend and prepop reverse:",l.reverse().bianli())