File size: 3,512 Bytes
2d5a722 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 | class DoublyLinkedBase:
class Node:
__slots__ = '_element', '_prev', '_next'
def __init__(self, element, prev, next):
self._element = element
self._prev = prev
self._next = next
def __init__(self):
self._header = self.Node(None, None, None)
self._trailer = self.Node(None, None, None)
self._header._next = self._trailer
self._trailer._prev = self._header
self._size = 0
def __len__(self):
return self._size
def is_empty(self):
return self._size == 0
def _insert_between(self, e, predecessor, successor):
newest = self.Node(e, predecessor, successor)
predecessor._next = newest
successor._prev = newest
self._size += 1
def insert_at_position(self, pos, e):
if pos < 1 or pos > self._size + 1:
print("Invalid position")
return
current = self._header
for _ in range(1, pos):
current = current._next
self._insert_between(e, current, current._next)
print("The element", e, "is successfully inserted at position", pos)
def _delete_node(self, node):
predecessor = node._prev
successor = node._next
predecessor._next = successor
successor._prev = predecessor
self._size -= 1
element = node._element
node._prev = node._next = node._element = None
return element
def delete_by_position(self, pos):
if pos < 1 or pos > self._size:
print("Invalid position")
return
current = self._header._next
for _ in range(1, pos):
current = current._next
removed = self._delete_node(current)
print("The element", removed, "is successfully removed")
def display(self):
if self.is_empty():
print("Doubly linked list is Empty!")
else:
current = self._header._next
print("Elements in Doubly linked list:")
while current != self._trailer:
print(current._element, "<->", end=" ")
current = current._next
print("NULL")
print("\t\tImplementation of Doubly Linked List ADT")
print("\t\t---------------------------------------")
dll = DoublyLinkedBase()
while True:
print("\n\tOPERATIONS")
print("1-Insertion at position")
print("2-Delete at position")
print("3-Length")
print("4-Is Empty")
print("5-Display")
print("6-Exit")
try:
ch = int(input("Enter your choice: "))
if ch == 1:
value = int(input("Enter an element: "))
pos = int(input("Enter position: "))
dll.insert_at_position(pos, value)
elif ch == 2:
if dll.is_empty():
print("Doubly linked list is empty!")
else:
pos = int(input("Enter position to delete: "))
dll.delete_by_position(pos)
elif ch == 3:
print("Number of elements:", len(dll))
elif ch == 4:
print("Is list empty?", dll.is_empty())
elif ch == 5:
dll.display()
elif ch == 6:
print("Program Exited")
break
else:
print("Invalid choice")
except ValueError:
print("Please enter a valid number")
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