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1ae5abfc3c
* Replace typing.optional with new annotations syntax
* updating DIRECTORY.md
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
85 lines
2.1 KiB
Python
85 lines
2.1 KiB
Python
"""
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Linked Lists consists of Nodes.
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Nodes contain data and also may link to other nodes:
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- Head Node: First node, the address of the
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head node gives us access of the complete list
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- Last node: points to null
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"""
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from __future__ import annotations
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from typing import Any
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class Node:
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def __init__(self, item: Any, next: Any) -> None:
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self.item = item
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self.next = next
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class LinkedList:
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def __init__(self) -> None:
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self.head: Node | None = None
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self.size = 0
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def add(self, item: Any) -> None:
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self.head = Node(item, self.head)
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self.size += 1
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def remove(self) -> Any:
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# Switched 'self.is_empty()' to 'self.head is None'
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# because mypy was considering the possibility that 'self.head'
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# can be None in below else part and giving error
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if self.head is None:
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return None
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else:
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item = self.head.item
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self.head = self.head.next
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self.size -= 1
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return item
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def is_empty(self) -> bool:
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return self.head is None
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def __str__(self) -> str:
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"""
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>>> linked_list = LinkedList()
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>>> linked_list.add(23)
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>>> linked_list.add(14)
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>>> linked_list.add(9)
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>>> print(linked_list)
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9 --> 14 --> 23
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"""
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if not self.is_empty:
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return ""
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else:
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iterate = self.head
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item_str = ""
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item_list: list[str] = []
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while iterate:
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item_list.append(str(iterate.item))
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iterate = iterate.next
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item_str = " --> ".join(item_list)
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return item_str
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def __len__(self) -> int:
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"""
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>>> linked_list = LinkedList()
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>>> len(linked_list)
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0
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>>> linked_list.add("a")
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>>> len(linked_list)
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1
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>>> linked_list.add("b")
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>>> len(linked_list)
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2
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>>> _ = linked_list.remove()
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>>> len(linked_list)
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1
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>>> _ = linked_list.remove()
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>>> len(linked_list)
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0
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"""
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return self.size
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