使用数据类的所有deque元素

Question

我很难让我的代码起作用。我正在尝试使用数据类获取所有deque元素，但这是行不通的。主要的德克是对的，但是他们的课出了点问题。

主德克

import Deque as deq

# Program starts
empty = deq.Deque()     # An empty deque
deque = deq.Deque()     # To be filled

for i in range(1, 11):
  deque.add_last(i)
print(deque.to_string())
print("Size:", deque.size)

for i in range(11, 21):
deque.add_first(i)
print(deque.to_string())
print("Size:", deque.size)

 print("\nget_last():", deque.get_last())
 print("get_last() on empty deque:", empty.get_last())

 print("\nget_first():", deque.get_first())
 print("get_first() on empty deque:", empty.get_first())

 print("\nremove_first():", deque.remove_first())
 print("remove_first() on empty deque:", empty.remove_first())

 print("\nremove_last():", deque.remove_last())
 print("remove_last() on empty deque:", empty.remove_last())

 print(deque.to_string())
 print("Size:", deque.size)

 print("\nTest to remove all elements")
 temp = deq.Deque()
 for i in range(100, 106):
   temp.add_first(i)
 print("After adding elements:", temp.to_string())
 while temp.size > 0:
   temp.remove_last()
 print("After removing all elements:", temp.to_string())
 print("Size:", temp.size)

这是Deque的课

from dataclasses import dataclass
from typing import Any



@dataclass
class Node:
value: int = None
nxt: Any = None  # Any since Node not properly defined at this point


@dataclass
class Deque:
   head: Node = None      # First node in queue
   tail: Node = None      # Last node in queue
   size: int = 0


 def add_last(self, n):
    new = Node(n, None)
    if self.head is None:
        self.head = new
        self.tail = new
    else:
        self.tail.nxt = new
        self.tail = new
    self.size += 1

def to_string(self):
    s = "{ "
    node = self.head
    while node is not None:
        s += str(node.value) + " "
        node = node.nxt
    s += "}"
    return s

def add_first(self, n):
    new = Node(n, None)
    if self.head is None:
        self.head = new
        self.tail = new
    else:
        self.tail.nxt = new
        self.tail = new
    self.size += 1

def get_last(self):
    if self.tail is None:
        print("Get can't be applied on an empty list")
        return None
    else:
        return self.tail.value


def get_first(self):
    pass


def remove_first(self):
    pass


def remove_last(self):
    pass

我得到的输出

None
Size: 0
None
Size: 0

get_last(): None
get_last() on empty deque: None

get_first(): None
get_first() on empty deque: None

remove_first(): None
remove_first() on empty deque: None

remove_last(): None
remove_last() on empty deque: None
None
Size: 0

Test to remove all elements
After adding elements: None
After removing all elements: None
Size: 0

我应该得到的输出

{ 1 2 3 4 5 6 7 8 9 10 }
Size: 10
{ 20 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 10 }
Size: 20

get_last(): 10
You can't access an empty queue
get_last() on empty deque: None

get_first(): 20
You can't access an empty queue
get_first() on empty deque: None

remove_first(): 20
You can't access an empty queue
remove_first() on empty deque: None

remove_last(): 10
You can't access an empty queue
remove_last() on empty deque: None
{ 19 18 17 16 15 14 13 12 11 1 2 3 4 5 6 7 8 9 }
Size: 18

Test to remove all elements
After adding elements: { 105 104 103 102 101 100 }
After removing all elements: { }
Size: 0

但是，我还没有完成整个代码，如果没有def add_first def add_last，我就无法启动。有人知道Deque类代码有什么问题吗？真的会把它当学徒

Answer 1

我想问题就在你的德克课上。在add_first和add_last方法中，没有正确地将新节点链接到列表的其余部分。

在add_first方法中，需要将新节点的下一个字段设置为指向列表的当前标题。然后，需要将Deque的head字段设置为指向新节点。

在add_last方法中，需要将新节点的下一个字段设置为None，因为它将是列表中的最后一个节点。然后，需要将Deque的尾部字段设置为指向新节点。

这是Deque类的固定代码。我希望这能帮到你。

从数据类型导入数据集输入任何

@dataclass
class Node:
value: int = None
nxt: Any = None  # Any since Node not properly defined at this point


@dataclass
class Deque:
   head: Node = None      # First node in queue
   tail: Node = None