链表

 '# -*- coding: utf-8 -*-'

class Lnode(object):
    # data:节点保存的数据
    # next:相当于next指针，指向下一个节点
    def __init__(self, data, pnext=None):
        self.data = data
        self.next = pnext

    def __repr__(self):
        # 用来定义node的字符输出
        return str(self.data)


class Linklist(object):
    def __init__(self):
        self.head = None
        self.length = 0

    # 在链表头部添加节点
    def prepend(self, value):
        if self.head is None:
            self.head = Lnode(value, None)
        else:
            newhead = Lnode(value, None)
            newhead.next = self.head
            self.head = newhead
            self.length += 1

    # 在链表尾部添加节点
    def append(self, value):
        if self.head is None:
            self.head = Lnode(value, None)
        else:
            cursor = self.head
            while cursor.next is not None:
                cursor = cursor.next
            cursor.next = Lnode(value, None)
            self.length += 1

    # 在链表的指定位置插入节点
    def insert(self, index, value):
        if self.head is None and index != 1:
            return
        if index <= 0 or index > self.getlength():
            return
        elif index == 1:
            self.prepend(value)
        elif index == self.getlength():
            self.append(value)
        else:
            cursor = self.head
            node = Lnode(value, None)
            for i in range(1, index - 1):
                cursor = cursor.next
            node.next = cursor.next
            cursor.next = node

    # 删除指定位置的节点
    def delnode(self, index):
        if self.head is None:
            return
        if index <= 0 or index > self.getlength():
            return
        elif index == 1:
            self.head = self.head.next
            self.length -= 1
        elif index == self.getlength():
            cursor = self.head
            for i in range(1, self.getlength() - 1):
                cursor = cursor.next
            cursor.next = None
            self.length -= 1
        else:
            cursor = self.head
            for i in range(1, index - 1):
                cursor = cursor.next
            t = cursor.next
            cursor.next = t.next
            self.length -= 1

    # 删除值为value的链表节点元素
    def delvalue(self, value):
        if self.head is None:
            return
        elif self.head.data == value:
            self.head = self.head.next
            self.length -= 1
        else:
            pre = self.head
            cursor = pre.next
            while cursor is not None:
                if cursor.data == value:
                    pre.next = cursor.next
                    cursor = cursor.next
                    self.length -= 1
                else:
                    pre = cursor
                    cursor = cursor.next

    # 按序号查找节点值
    def getindex(self, index):
        if self.head is None:
            return
        elif index <= 0 or index > self.getlength():
            return
        elif index == 1:
            return self.head.data
        else:
            cursor = self.head
            for i in range(1, index):
                cursor = cursor.next
            return cursor.data
        # else:
        #     counter = 1
        #     cursor = self.head
        #     while cursor is not None:
        #         if index == counter:
        #             return cursor.data
        #         else:
        #             counter += 1
        #             cursor = cursor.next

    # 求链表的长度
    def getlength(self):
        if self.head is None:
            return 0
        else:
            count = 1
            cursor = self.head
            while cursor.next is not None:
                count += 1
                cursor = cursor.next
        return count

    # 单链表逆序
    def diverse(self):
        if self.head is None:
            return
        elif self.head.next is None:
            return self.head
        else:
            pre = None
            cursor = self.head
            while cursor is not None:
                ne = cursor.next
                cursor.next = pre
                pre = cursor
                cursor = ne
            self.head = pre

    # 删除链表中重复元素
    def delrepret(self):
        if self.head is None:
            return
        if self.head.next is None:
            return self.head
        else:
            data = self.head.data
            # print(data)
            count = 1
            dic = {data: 1}
            pre = self.head
            cursor = pre.next
            while cursor is not None:
                print(cursor.data)
                if dic.get(cursor.data) is None:
                    dic[cursor.data] = dic.setdefault(cursor.data, 1)
                    pre = cursor
                    cursor = cursor.next
                    print(dic)
                else:
                    pre.next = cursor.next
                    cursor = cursor.next
                    self.length -= 1

    # 判断链表是否为空
    def isempty(self):
        if self.head is None or self.getlength() == 0:
            return True
        else:
            return False

    # 删除列表
    def dellist(self):
        if self.head is None or self.getlength() == 0:
            return
        else:
            cursor = self.head
            while cursor is not None:
                cursor.data = None
                cursor = cursor.next
            self.head = None

    # 打印链表元素
    def print(self):
        if self.head is None:
            return
        else:
            cursor = self.head
            while cursor is not None:
                print(cursor.data, end=' ')
                cursor = cursor.next
            print()


if __name__ == "__main__":

    linklist = Linklist()
    print(linklist.isempty())
    for i in range(1, 5):
        linklist.append(i)
    linklist.prepend(1)
    linklist.print()
    print("按序号查找")
    print(linklist.getindex(4))
    print("&&&&&&&&&&&&&&&&")
    linklist.insert(3, 5)
    linklist.print()
    linklist.insert(1, 1)
    linklist.print()
    linklist.insert(2, 2)
    print(linklist.isempty())
    linklist.print()
    print("删除重复元素")
    linklist.delrepret()
    print("输出删除元素后的链表")
    linklist.print()
    # linklist.diverse()
    # linklist.print()
    linklist.delnode(5)
    # linklist.delvalue(5)
    # print("&&&&&&&&&&&&")
    # linklist.print()
    # print("**********")
    # linklist.dellist()
    # print("@@@@@@@@@@@@")
    # length = linklist.getlength()
    # print(length)
    linklist.print()