链表简介与数据结构
单向链表也叫单链表，是表中最简单的一种形式，它的每个节点包含两个域，一个信息域（元素域）和一个链接域。这个链接指向链表中的下一个节点，而最后一个节点的链接域则指向一个空值。
单向链表的抽象数据类型定义：
. 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
链表的定义
1 class Node(object): 2 def __init__(self, item): 3 self.item = item 4 self.next = None 5 6 7 class Link(object): 8 def __init__(self): 9 self._head = None 10 11 def isEmpty(self): 12 return self._head is None 13 14 @property 15 def length(self): 16 node = self._head 17 count = 0 18 while node: 19 count += 1 20 node = node.next 21 return count 22 23 def travel(self): 24 if self._head: 25 cur_node = self._head 26 while cur_node: 27 print(cur_node.item) 28 cur_node = cur_node.next 29 else: 30 raise ("<The object is empty!>") 31 32 def add(self, item): 33 node = Node(item) 34 node.next = self._head 35 self._head = node 36 37 def append(self, item): 38 node = Node(item) 39 if self.isEmpty(): 40 self._head = node 41 else: 42 cur_node = self._head 43 while cur_node: 44 pre_node, cur_node = cur_node, cur_node.next 45 pre_node.next = node 46 47 def insert(self, item, index): 48 if index <= 0: # 插入位置索引小于等于0都是在头部插入 49 self.add(item) 50 elif index >= self.length: # 插入位置索引大于等于链表长度时都是在尾部插入 51 self.append(item) 52 else: # 插入位置索引index在1到链表length-1之间 53 node = Node(item) 54 cur_node = self._head.next 55 pre = self._head 56 count = 1 57 while cur_node: 58 if count == index: 59 pre.next, node.next = node, cur_node 60 break 61 pre, cur_node = cur_node, cur_node.next 62 count += 1 63 64 def remove(self, item): 65 if self.isEmpty(): # 空提示 66 return "Failed because of Empty!" 67 cur_node = self._head 68 pre_node = None 69 while cur_node: 70 if cur_node.item == item: 71 if pre_node == None: # 删除的索引为0 72 self._head = cur_node.next 73 else: 74 pre_node.next = cur_node.next 75 return item 76 pre_node, cur_node = cur_node, cur_node.next 77 raise ("Not found!") # 最后没有找到报错 78 79 def search(self, item): 80 if self.isEmpty(): 81 raise ("<The object is empty!>") 82 else: 83 cur_node = self._head 84 index = 0 85 while cur_node: 86 if cur_node.item == item: 87 return index 88 index += 1 89 cur_node = cur_node.next 90 return -1
链表的使用
1 link = Link() 2 link.append(2) 3 link.append(3) 4 link.add(4) 5 link.insert(11, 1) 6 link.remove(4) 7 link.travel() 8 print(link.length) 9 print(link.search(11))