22 - python & all web labs

labPython/lab21/task_5.py

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+class Node:
+    def __init__(self, value):
+        self.value = value
+        self.next = None
+        self.prev = None
+
+
+class DoublyCircularList:
+    def __init__(self):
+        self.head = None
+
+    def append(self, value):
+        new_node = Node(value)
+        if not self.head:
+            self.head = new_node
+            new_node.next = new_node
+            new_node.prev = new_node
+        else:
+            tail = self.head.prev
+            tail.next = new_node
+            new_node.prev = tail
+            new_node.next = self.head
+            self.head.prev = new_node
+
+    def __iter__(self):
+        return ReverseIterator(self.head)
+
+
+class ReverseIterator:
+    def __init__(self, head):
+        self.current = head.prev if head else None
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        if not self.current:
+            raise StopIteration
+        val = self.current.value
+        self.current = self.current.prev
+        return val
+
+
+while True:
+    print("1 - Создать список и начать итерацию")
+    print("0 - Выход")
+    choice = input("Выбор: ")
+
+    if choice == "0":
+        break
+
+    if choice == "1":
+        try:
+            data = input("Введите элементы через пробел: ").split()
+            lst = DoublyCircularList()
+            for x in data:
+                lst.append(x)
+
+            it = iter(lst)
+            n = int(input("Сколько элементов вывести: "))
+            for _ in range(n):
+                print(next(it))
+        except:
+            print("Ошибка")