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  • python单链表

    #!/usr/bin/env python3
    # -*- coding:utf-8 -*-
    
    
    class LNode:
        """
        结点类
        """
    
        def __init__(self, elem, next_=None):
            self.elem = elem
            self.next = next_
    
    
    class LinkedListUnderflow(ValueError):
        """
        自定义异常
        """
        pass
    
    
    class LList:
        """
        链表类
        """
    
        def __init__(self):
            self._head = None
    
        def is_empty(self):
            return self._head is None
    
        # 操作pop删除表头结点并返回这个结点里的数据
        def pop(self):
            if self._head is None:
                raise LinkedListUnderflow("in pop")
            e = self._head.elem
            self._head = self._head.next
            return e
    
        # 在表头插入元素
        def prepend(self, elem):
            self._head = LNode(elem, self._head)
    
        # 在链表最后插入元素
        def append(self, elem):
            if self._head is None:
                self._head = LNode(elem)
                return None
            # 如果链表为空则直接把表头指向需要插入的元素即可在。实际上是在操作_head域
    
            p = self._head
            while p.next is not None:
                p = p.next
            p.next = LNode(elem)
            # 如果不为空,则先从头扫描链表,找到最后的结点,然后把最后结点的next指向需要插入的元素即可。实际上是在操作next域
    
        # 删除最后一个结点
        def pop_last(self):
            if self._head is None:  # 空表
                raise LinkedListUnderflow("in pop_last")
            p = self._head
            if p.next is None:  # 如果表长为1,则清空之,并返回原来的元素
                e = p.elem
                self._head = None
                return e
            while p.next.next is not None:
                p = p.next
            e = p.next.elem
            p.next = None
            return e
            # 如果表长大于1,则从头扫描,找到倒数第二个结点,把倒数第二个结点的next域置空,并返回最后一个结点
    
        def printall(self):  # 扫描打印链表的每个元素
            p = self._head
            while p is not None:
                print(p.elem, end='')
                if p.next is not None:
                    print(',', end='')
                p = p.next
    
        def elements(self):  # 写一个生成器,使链表支持for操作
            p = self._head
            while p is not None:
                yield p.elem
                p = p.next
    
    
    class LList1(LList):  # 派生一个变形单链表类
        def __init__(self):
            LList.__init__(self)
            self._rear = None
    
        def prepend(self, elem):  # 重构prepend方法
            if self._rear is None:
                self._head = LNode(elem, self._head)
                self._rear = self._head
            else:
                self._head = LNode(elem, self._head)
    
        def append(self, elem):
            if self._head is None:
                self._head = LNode(elem, self._head)
                self._rear = self._head
            else:
                self._rear.next = LNode(elem)
                self._rear = self._rear.next
    
        def pop_last(self):
            if self._head is None:
                raise LinkedListUnderflow("in pop_last")
            p = self._head
            if p.next is None:
                self._head = None
                return p.elem
            while p.next.next is not None:
                p = p.next
            e = p.next.elem
            p.next = None
            self._rear = p
            return e
    
    
    
    
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  • 原文地址:https://www.cnblogs.com/whatisfantasy/p/6548546.html
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