I am learning about LinkedList. I ran this once. But when I am trying to run this code once again It didn't work out. I wonder why. The error shows when I'm trying to call the method "remove" Firstly, a class of linkedlist has been created. And then we add new method to this class. The method "addFirst" is used to insert element at the beginning of the linkedlist. On the other hand, the method "addLast" is used to insert element at the end of the linkedlist. "addAfter" is used to insert element after a target node. Similar to the method "addBefore" While method "remove" is used to remove a node in the linkedlist.

class LinkedList:
    def __init__(self):
        self.head = None

    def __repr__(self):
        node = self.head
        nodes = []
        while node is not None:
          nodes.append(node.data)
          node = node.next
        nodes.append("None")
        return " -> ".join(nodes)

    def __iter__(self):
        node = self.head
        while node is not None:
          yield node
          node = node.next

    def add_first(self, node):
        node.next = self.head
        self.head = node

    def add_last(self, node):
        if self.head is None:
            self.head = node
            return
        for current_node in self:
            pass
        current_node.next = node

    def add_after(self, target_node_data, new_node):
        if self.head is None:
          raise Exception("List is empty")
        for node in self:
          if node.data == target_node_data:
            new_node.next = node.next
            node.next = new_node
            return
        raise Exception("Target not found")

    def add_before(self, target_node_data, new_node):
        if self.head is None:
            raise Exception("List is empty")
        if self.head.data == target_node_data:
            return self.add_first(new_node)
        prev_node = self.head
        for node in self:
            if node.data == target_node_data:
                prev_node.next = new_node
                new_node.next = node
                return
            prev_node = node
        raise Exception("Target Node not found")

    def remove_node(self, target_node_data):
         if self.head is None:
          raise Exception("List is empty")

         if self.head.data == target_node_data:
          self.head = self.head.next
          return

         previous_node = self.head
         for node in self:
          if node.data == target.node.data:
            previous_node.next = node.next
            node.next = None
            return
          previous_node = node
        
         raise Exception("Target Node not found")


class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

    def __repr__(self):
        return self.data


llist = LinkedList()
first_node = Node("a")
llist.head = first_node
second_node = Node("b")
third_node = Node("c")
first_node.next = second_node
second_node.next = third_node
for node in llist:
  print(node)


llist.add_first(Node("b2"))
llist

llist.add_last(Node("b"))
llist

llist.add_after("a", Node("b"))
llist

llist.remove_node("a")

CodePudding user response：

Should be target_node_data not target.node.data:

class LinkedList:
    def __init__(self):
        self.head = None

    def __repr__(self):
        node = self.head
        nodes = []
        while node is not None:
            nodes.append(node.data)
            node = node.next
        nodes.append("None")
        return " -> ".join(nodes)

    def __iter__(self):
        node = self.head
        while node is not None:
            yield node
            node = node.next

    def add_first(self, node):
        node.next = self.head
        self.head = node

    def add_last(self, node):
        if self.head is None:
            self.head = node
            return
        for current_node in self:
            pass
        current_node.next = node

    def add_after(self, target_node_data, new_node):
        if self.head is None:
            raise Exception("List is empty")
        for node in self:
            if node.data == target_node_data:
                new_node.next = node.next
                node.next = new_node
                return
        raise Exception("Target not found")

    def add_before(self, target_node_data, new_node):
        if self.head is None:
            raise Exception("List is empty")
        if self.head.data == target_node_data:
            return self.add_first(new_node)
        prev_node = self.head
        for node in self:
            if node.data == target_node_data:
                prev_node.next = new_node
                new_node.next = node
                return
            prev_node = node
        raise Exception("Target Node not found")

    def remove_node(self, target_node_data):
        if self.head is None:
            raise Exception("List is empty")

        if self.head.data == target_node_data:
            self.head = self.head.next
            return

        previous_node = self.head
        for node in self:
            if node.data == target_node_data:
                previous_node.next = node.next
                node.next = None
                return
            previous_node = node

        raise Exception("Target Node not found")


class Node:
    def __init__(self, data):
        self.data = data
        self.next = None

    def __repr__(self):
        return self.data


llist = LinkedList()
first_node = Node("a")
llist.head = first_node
second_node = Node("b")
third_node = Node("c")
first_node.next = second_node
second_node.next = third_node
for node in llist:
    print(node)

llist.add_first(Node("b2"))
llist

llist.add_last(Node("b"))
llist

llist.add_after("a", Node("b"))
llist

llist.remove_node("a")