# coding:utf-8# 单链表的相关操作：
# is_empty() 链表是否为空
# length() 链表长度
# travel() 遍历整个链表
# add(item) 链表头部添加元素
# append(item) 链表尾部添加元素
# insert(pos, item) 指定位置添加元素
# remove(item) 删除节点
# search(item) 查找节点是否存在class Node(object):"""节点"""def __init__(self, elem):# 数据区self.elem = elem# 指向下一个节点self.next = Noneclass SingleLikedList(object):"""单链表"""def __init__(self, node = None):# 头节点self.__head = nodedef is_empty(self):"""链表是否为空"""return self.__head is Nonedef length(self):"""链表长度"""cur = self.__headcount = 0while cur != None:count += 1cur = cur.nextreturn countdef travel(self):"""遍历整个链表"""cur = self.__headwhile cur != None:print(cur.elem, end=" ")cur = cur.nextprint("")def add(self, item):"""链表头部添加元素，头插法"""# 创建一个Nodenode = Node(item)node.next = self.__headself.__head = nodedef append(self, item):"""链表尾部添加元素，尾插法"""# 创建一个Nodenode = Node(item)# 如果链表为空if self.is_empty():self.__head = nodeelse:cur = self.__headwhile cur.next != None:cur = cur.nextcur.next = nodedef insert(self, pos, item):"""指定位置添加元素:param pos 从0开始"""if pos <= 0:self.add(item)elif pos > (self.length() - 1):self.append(item)else:pre = self.__headcount = 0# 1 2 3 4 5 6# pos = 3, item = 9while count < (pos - 1):count += 1pre = pre.next# 当循环结束后，pre指向要插入位置的前一个，即pos-1的位置node = Node(item)node.next = pre.nextpre.next = nodedef remove(self, item):"""删除节点"""pre = Nonecur = self.__headwhile cur != None:if cur.elem == item:# 判断此节点是否为头节点if cur == self.__head:self.__head = cur.nextelse:pre.next = cur.nextbreakelse:pre = curcur = cur.nextdef search(self,item):"""查找节点是否存在"""cur = self.__headwhile cur != None:if cur.elem == item:return Trueelse:cur = cur.nextreturn Falseif __name__ == "__main__":sll = SingleLikedList()print("initialized...")print("is_empty:", sll.is_empty())print("length:", sll.length())sll.append(1)print("is_empty:", sll.is_empty())print("length:", sll.length())sll.append(2)sll.append(3)sll.append(4)sll.append(5)sll.append(6)sll.add(7)sll.travel()print("before insert exist -5:",sll.search(-5))sll.insert(-5, -5)print("after insert exist -5:", sll.search(-5))sll.travel()