python算法与数据结构-单链表

小灰灰 2023-10-06 12:29 11阅读 0赞

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70][]

单向链表定义如下所示:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 1][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 2][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 3][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 4][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 5][]

在头部插入元素如下所示：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 6][]

头部插入元素最终达到的效果，先改变指向100的节点，再改变指向头部的节点(这个有先后顺序)，这样以前100之后的节点顺序什么的就不用改变了

在指定位置插入元素，如下所示:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 7][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 8][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 9][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 10][]

单链表查找元素如下所示:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 11][]

单链表删除元素如下所示:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 12][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 13][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 14][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 15][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 16][]

头节点是删除的节点的时候，如下所示:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 17][]

还有一种情况是只有一个节点的时候，如下所示:

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 18][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 19][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2diNDIxNTI4Nw_size_16_color_FFFFFF_t_70 20][]

代码如下所示:

# -*-coding=utf-8-*-
    class Node(object):
        """单链表的节点"""
        def __init__(self, elem):
            # item存放数据元素
            self.elem = elem
            # next是下一个节点的标识
            self.next = None
    
    
    class SingleLinkList(object):
        """单链表"""
        # head是头节点属性,_head在Python中加两个下划线就是私有属性
        # 这个node是用户传进来的
        def __init__(self, node=None):
            self.__head = node
    
        def is_empty(self):
            """判断是否为空"""
            return self.__head==None
    
        def length(self):
            """链表长度"""
            # cur初始时指向头节点
            # cur游标，用来移动遍历节点
            cur = self.__head  # 这里是一个下划线还是两个待确定
            # count 记录数量
            count = 0
            # 当cur.next != None，表示始终进入循环体，因为cur.next需要在循环体里面才能知道是多少
            # 尾节点指向None，当未到达尾部时
            while cur != None:
                count += 1
                # 将cur后移一个节点
                cur = cur.next
            return count
    
        def travel(self):
            """遍历整个链表"""
            cur = self.__head
            while cur != None:
                #添加这个这个，后期打印就不换行了
                print(cur.elem,end=" ")
                cur = cur.next
            print("")
            # pass
    
        def append(self, item):
            """链表尾部添加元素，尾插法"""
            node = Node(item)
            # print('node值是:')
            # print(node)
            # 这个if条件是空链表的意思，我们需要考虑特殊条件
            # 先判断链表是否为空，若是空链表，则将_head指向新节点
            if self.is_empty(): #赋值为空不然会报错
                self.__head = node
            # 若不为空，则找到尾部，将尾节点的next指向新节点
            else:
                # print("222")
                # cur = self.__head
                cur = self.__head
                while cur.next != None:
                    cur = cur.next
                cur.next = node  # 到最后一个位置将元素赋值
        def add(self,item):
            """链表头部添加元素，头插法"""
            # 先创建一个保存item值的节点
            node = Node(item)
            # 将新节点的链接域next指向头节点，即_head指向的位置
            node.next = self.__head
            # 将链表的头_head指向新节点
            self.__head = node
        #pos是指定的位置,item是保存的元素
        def insert(self,pos,item):
            """链表指定位置添加元素
            :param pos 从0开始
            """
            # 若指定位置pos为第一个元素之前，则执行头部插入
            if pos<=0: #头插法
                self.add(item)
            # 若指定位置超过链表尾部，则执行尾部插入
            elif pos > (self.length()-1):#尾插法
                self.append(item)
            # 找到指定位置
            else:
                # pre用来指向指定位置pos的前一个位置pos-1，初始从头节点开始移动到指定位置
                prev = self.__head
                count = 0
                while count<(pos-1):
                    count+=1
                    prev = prev.next
                #当循环退出后,prev指向pos-1位置
                node = Node(item)
                # 先将新节点node的next指向插入位置的节点
                #prev.next存储的是下一个节点的地址，因为是在任意位置插入的，新节点node需要连接下一个节点，node.next指向了下一个节点
                node.next = prev.next
                # 将插入位置的前一个节点的next指向新节点
                prev.next = node
        def search(self,item):
            """查找节点是否存在"""
            """链表查找节点是否存在，并返回True或者False"""
            cur = self.__head
            while cur!=None:
                if cur.elem == item:
                     return  True
                else:
                    cur = cur.next
            return False
        def remove(self,item):
            """删除节点"""
            cur = self.__head
            pre = None
            while cur != None:
                # 找到了指定元素
                if cur.elem == item:
                    #先判断此节点是否是头节点
                    #头节点 # 如果第一个就是删除的节点
                    if cur == self.__head:
                        # 将头指针指向头节点的后一个节点
                         self.__head = cur.next
                    else:
                         # 将删除位置前一个节点的next指向删除位置的后一个节点
                         pre.next = cur.next
                    break  # 删除后再退出循环,需要一个总的break退出
                else:
                    # 继续按链表后移节点
                    pre = cur
                    cur = cur.next
    
    
    if __name__ == "__main__":
        # node = Node(100)
        ll = SingleLinkList()
        print(ll.is_empty()) #True
        print(ll.length())   #0
    
        ll.append(1)
        print(ll.is_empty()) #False
        print(ll.length())   #1
        #
        ll.append(2)
        ll.add(8)
        ll.append(3)
        ll.append(4)
        ll.append(5)
        ll.append(6)
        #8 1 2 3 4 5 6
        ll.insert(-1,9)
        ll.travel()      #9 8 1 2 3 4 5 6
        ll.insert(3, 100)
        ll.travel()      #9 8 1 100 2 3 4 5 6
        ll.insert(10,200)
        ll.travel()      #9 8 1 100 2 3 4 5 6 200
        ll.remove(100)
        ll.travel()      #9 8 1 2 3 4 5 6 200
        ll.remove(9)
        ll.travel()      #8 1 2 3 4 5 6 200
        ll.remove(200)
        ll.travel()      #8 1 2 3 4 5 6

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