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Updated circular_linked_list (#2483)
* Updated circular_linked_list
* fixup! Format Python code with psf/black push
* Update data_structures/linked_list/circular_linked_list.py
Co-authored-by: Christian Clauss <cclauss@me.com>
* updating DIRECTORY.md
* delete print_list()
* test is_empty()
* test is_empty return False
* fixup! Format Python code with psf/black push
* fixed indentation
* fixup! Format Python code with psf/black push
Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>
Co-authored-by: Christian Clauss <cclauss@me.com>
This commit is contained in:
Du Yuanchao
GitHub
parent
db0db01d87
commit
7f48bb8c95
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@ -2,201 +2,137 @@ from typing import Any
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class Node:
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"""
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Class to represent a single node.
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Each node has following attributes
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* data
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* next_ptr
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"""
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def __init__(self, data: Any):
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self.data = data
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self.next_ptr = None
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self.next = None
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class CircularLinkedList:
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"""
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Class to represent the CircularLinkedList.
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CircularLinkedList has following attributes.
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* head
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* length
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"""
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def __init__(self):
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self.head = None
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self.length = 0
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self.tail = None
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def __iter__(self):
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node = self.head
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while self.head:
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yield node.data
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node = node.next
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if node == self.head:
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break
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def __len__(self) -> int:
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"""
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Dunder method to return length of the CircularLinkedList
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>>> cll = CircularLinkedList()
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>>> len(cll)
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0
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>>> cll.append(1)
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>>> len(cll)
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1
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>>> cll.prepend(0)
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>>> len(cll)
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2
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>>> cll.delete_front()
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>>> len(cll)
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1
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>>> cll.delete_rear()
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>>> len(cll)
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0
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"""
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return self.length
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return len(tuple(iter(self)))
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def __str__(self) -> str:
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"""
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Dunder method to represent the string representation of the CircularLinkedList
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>>> cll = CircularLinkedList()
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>>> print(cll)
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Empty linked list
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>>> cll.append(1)
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>>> cll.append(2)
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>>> print(cll)
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<Node data=1> => <Node data=2>
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"""
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current_node = self.head
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if not current_node:
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return "Empty linked list"
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def __repr__(self):
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return "->".join(str(item) for item in iter(self))
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results = [current_node.data]
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current_node = current_node.next_ptr
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def insert_tail(self, data: Any) -> None:
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self.insert_nth(len(self), data)
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while current_node != self.head:
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results.append(current_node.data)
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current_node = current_node.next_ptr
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return " => ".join(f"<Node data={result}>" for result in results)
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def append(self, data: Any) -> None:
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"""
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Adds a node with given data to the end of the CircularLinkedList
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>>> cll = CircularLinkedList()
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>>> cll.append(1)
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>>> print(f"{len(cll)}: {cll}")
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1: <Node data=1>
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>>> cll.append(2)
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>>> print(f"{len(cll)}: {cll}")
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2: <Node data=1> => <Node data=2>
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"""
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current_node = self.head
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def insert_head(self, data: Any) -> None:
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self.insert_nth(0, data)
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def insert_nth(self, index: int, data: Any) -> None:
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if index < 0 or index > len(self):
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raise IndexError("list index out of range.")
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new_node = Node(data)
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new_node.next_ptr = new_node
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if current_node:
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while current_node.next_ptr != self.head:
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current_node = current_node.next_ptr
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current_node.next_ptr = new_node
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new_node.next_ptr = self.head
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if self.head is None:
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new_node.next = new_node # first node points itself
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self.tail = self.head = new_node
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elif index == 0: # insert at head
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new_node.next = self.head
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self.head = self.tail.next = new_node
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else:
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self.head = new_node
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temp = self.head
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for _ in range(index - 1):
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temp = temp.next
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new_node.next = temp.next
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temp.next = new_node
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if index == len(self) - 1: # insert at tail
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self.tail = new_node
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self.length += 1
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def delete_front(self):
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return self.delete_nth(0)
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def prepend(self, data: Any) -> None:
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"""
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Adds a node with given data to the front of the CircularLinkedList
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>>> cll = CircularLinkedList()
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>>> cll.prepend(1)
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>>> cll.prepend(2)
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>>> print(f"{len(cll)}: {cll}")
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2: <Node data=2> => <Node data=1>
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"""
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current_node = self.head
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def delete_tail(self) -> None:
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return self.delete_nth(len(self) - 1)
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new_node = Node(data)
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new_node.next_ptr = new_node
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if current_node:
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while current_node.next_ptr != self.head:
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current_node = current_node.next_ptr
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current_node.next_ptr = new_node
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new_node.next_ptr = self.head
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self.head = new_node
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self.length += 1
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def delete_front(self) -> None:
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"""
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Removes the 1st node from the CircularLinkedList
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>>> cll = CircularLinkedList()
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>>> cll.delete_front()
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Traceback (most recent call last):
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...
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IndexError: Deleting from an empty list
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>>> cll.append(1)
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>>> cll.append(2)
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>>> print(f"{len(cll)}: {cll}")
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2: <Node data=1> => <Node data=2>
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>>> cll.delete_front()
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>>> print(f"{len(cll)}: {cll}")
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1: <Node data=2>
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>>> cll.delete_front()
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>>> print(f"{len(cll)}: {cll}")
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0: Empty linked list
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"""
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if not self.head:
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raise IndexError("Deleting from an empty list")
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current_node = self.head
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if current_node.next_ptr == current_node:
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self.head = None
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def delete_nth(self, index: int = 0):
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if not 0 <= index < len(self):
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raise IndexError("list index out of range.")
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delete_node = self.head
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if self.head == self.tail: # just one node
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self.head = self.tail = None
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elif index == 0: # delete head node
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self.tail.next = self.tail.next.next
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self.head = self.head.next
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else:
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while current_node.next_ptr != self.head:
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current_node = current_node.next_ptr
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temp = self.head
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for _ in range(index - 1):
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temp = temp.next
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delete_node = temp.next
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temp.next = temp.next.next
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if index == len(self) - 1: # delete at tail
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self.tail = temp
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return delete_node.data
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current_node.next_ptr = self.head.next_ptr
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self.head = self.head.next_ptr
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def is_empty(self):
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return len(self) == 0
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self.length -= 1
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if not self.head:
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assert self.length == 0
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def delete_rear(self) -> None:
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def test_circular_linked_list() -> None:
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"""
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Removes the last node from the CircularLinkedList
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>>> cll = CircularLinkedList()
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>>> cll.delete_rear()
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Traceback (most recent call last):
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...
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IndexError: Deleting from an empty list
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>>> cll.append(1)
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>>> cll.append(2)
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>>> print(f"{len(cll)}: {cll}")
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2: <Node data=1> => <Node data=2>
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>>> cll.delete_rear()
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>>> print(f"{len(cll)}: {cll}")
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1: <Node data=1>
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>>> cll.delete_rear()
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>>> print(f"{len(cll)}: {cll}")
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0: Empty linked list
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>>> test_circular_linked_list()
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"""
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if not self.head:
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raise IndexError("Deleting from an empty list")
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circular_linked_list = CircularLinkedList()
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assert len(circular_linked_list) == 0
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assert circular_linked_list.is_empty() is True
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assert str(circular_linked_list) == ""
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temp_node, current_node = self.head, self.head
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try:
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circular_linked_list.delete_front()
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assert False # This should not happen
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except IndexError:
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assert True # This should happen
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if current_node.next_ptr == current_node:
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self.head = None
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else:
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while current_node.next_ptr != self.head:
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temp_node = current_node
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current_node = current_node.next_ptr
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try:
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circular_linked_list.delete_tail()
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assert False # This should not happen
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except IndexError:
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assert True # This should happen
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temp_node.next_ptr = current_node.next_ptr
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try:
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circular_linked_list.delete_nth(-1)
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assert False
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except IndexError:
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assert True
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self.length -= 1
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if not self.head:
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assert self.length == 0
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try:
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circular_linked_list.delete_nth(0)
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assert False
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except IndexError:
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assert True
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assert circular_linked_list.is_empty() is True
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for i in range(5):
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assert len(circular_linked_list) == i
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circular_linked_list.insert_nth(i, i + 1)
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assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 6))
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circular_linked_list.insert_tail(6)
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assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 7))
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circular_linked_list.insert_head(0)
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assert str(circular_linked_list) == "->".join(str(i) for i in range(0, 7))
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assert circular_linked_list.delete_front() == 0
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assert circular_linked_list.delete_tail() == 6
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assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 6))
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assert circular_linked_list.delete_nth(2) == 3
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circular_linked_list.insert_nth(2, 3)
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assert str(circular_linked_list) == "->".join(str(i) for i in range(1, 6))
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assert circular_linked_list.is_empty() is False
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if __name__ == "__main__":
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