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134 lines
3.7 KiB
Python
134 lines
3.7 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: # noqa: A002
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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, position: int = 0) -> None:
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"""
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Add an item to the LinkedList at the specified position.
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Default position is 0 (the head).
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Args:
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item (Any): The item to add to the LinkedList.
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position (int, optional): The position at which to add the item.
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Defaults to 0.
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Raises:
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ValueError: If the position is negative or out of bounds.
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>>> linked_list = LinkedList()
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>>> linked_list.add(1)
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>>> linked_list.add(2)
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>>> linked_list.add(3)
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>>> linked_list.add(4, 2)
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>>> print(linked_list)
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3 --> 2 --> 4 --> 1
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# Test adding to a negative position
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>>> linked_list.add(5, -3)
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Traceback (most recent call last):
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...
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ValueError: Position must be non-negative
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# Test adding to an out-of-bounds position
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>>> linked_list.add(5,7)
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Traceback (most recent call last):
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...
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ValueError: Out of bounds
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>>> linked_list.add(5, 4)
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>>> print(linked_list)
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3 --> 2 --> 4 --> 1 --> 5
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"""
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if position < 0:
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raise ValueError("Position must be non-negative")
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if position == 0 or self.head is None:
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new_node = Node(item, self.head)
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self.head = new_node
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else:
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current = self.head
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for _ in range(position - 1):
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current = current.next
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if current is None:
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raise ValueError("Out of bounds")
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new_node = Node(item, current.next)
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current.next = new_node
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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 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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