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Updated singly_linked_list (#2477)
* Updated singly_linked_list
* fixup! Format Python code with psf/black push
* undo __repr__
* updating DIRECTORY.md
* UNTESTED CHANGES: Add an .__iter__() method.
This will break tests, etc.
* fixup! Format Python code with psf/black push
* len(tuple(iter(self)))
* fixed __repr__()
* Update data_structures/linked_list/singly_linked_list.py
Co-authored-by: Christian Clauss <cclauss@me.com>
* Update data_structures/linked_list/singly_linked_list.py
Co-authored-by: Christian Clauss <cclauss@me.com>
* Update data_structures/linked_list/singly_linked_list.py
Co-authored-by: Christian Clauss <cclauss@me.com>
* Update data_structures/linked_list/singly_linked_list.py
Co-authored-by: Christian Clauss <cclauss@me.com>
* Update data_structures/linked_list/singly_linked_list.py
Co-authored-by: Christian Clauss <cclauss@me.com>
* Update data_structures/linked_list/singly_linked_list.py
Co-authored-by: Christian Clauss <cclauss@me.com>
* Update data_structures/linked_list/singly_linked_list.py
Co-authored-by: Christian Clauss <cclauss@me.com>
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
a196a36514
commit
18f1dcd48a
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@ -25,7 +25,9 @@
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* [Sum Of Subsets](https://github.com/TheAlgorithms/Python/blob/master/backtracking/sum_of_subsets.py)
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## Bit Manipulation
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* [Binary And Operator](https://github.com/TheAlgorithms/Python/blob/master/bit_manipulation/binary_and_operator.py)
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* [Binary Or Operator](https://github.com/TheAlgorithms/Python/blob/master/bit_manipulation/binary_or_operator.py)
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* [Binary Xor Operator](https://github.com/TheAlgorithms/Python/blob/master/bit_manipulation/binary_xor_operator.py)
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## Blockchain
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* [Chinese Remainder Theorem](https://github.com/TheAlgorithms/Python/blob/master/blockchain/chinese_remainder_theorem.py)
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@ -9,105 +9,15 @@ class Node:
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class LinkedList:
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def __init__(self):
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self.head = None # initialize head to None
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self.head = None
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def insert_tail(self, data) -> None:
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if self.head is None:
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self.insert_head(data) # if this is first node, call insert_head
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else:
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temp = self.head
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while temp.next: # traverse to last node
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temp = temp.next
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temp.next = Node(data) # create node & link to tail
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def __iter__(self):
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node = self.head
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while node:
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yield node.data
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node = node.next
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def insert_head(self, data) -> None:
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new_node = Node(data) # create a new node
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if self.head:
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new_node.next = self.head # link new_node to head
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self.head = new_node # make NewNode as head
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def print_list(self) -> None: # print every node data
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temp = self.head
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while temp:
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print(temp.data)
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temp = temp.next
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def delete_head(self): # delete from head
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temp = self.head
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if self.head:
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self.head = self.head.next
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temp.next = None
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return temp
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def delete_tail(self): # delete from tail
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temp = self.head
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if self.head:
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if self.head.next is None: # if head is the only Node in the Linked List
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self.head = None
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else:
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while temp.next.next: # find the 2nd last element
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temp = temp.next
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# (2nd last element).next = None and temp = last element
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temp.next, temp = None, temp.next
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return temp
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def is_empty(self) -> bool:
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return self.head is None # return True if head is none
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def reverse(self):
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prev = None
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current = self.head
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while current:
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# Store the current node's next node.
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next_node = current.next
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# Make the current node's next point backwards
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current.next = prev
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# Make the previous node be the current node
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prev = current
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# Make the current node the next node (to progress iteration)
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current = next_node
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# Return prev in order to put the head at the end
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self.head = prev
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def __repr__(self): # String representation/visualization of a Linked Lists
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current = self.head
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string_repr = ""
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while current:
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string_repr += f"{current} --> "
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current = current.next
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# END represents end of the LinkedList
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return string_repr + "END"
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# Indexing Support. Used to get a node at particular position
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def __getitem__(self, index):
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current = self.head
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# If LinkedList is empty
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if current is None:
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raise IndexError("The Linked List is empty")
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# Move Forward 'index' times
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for _ in range(index):
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# If the LinkedList ends before reaching specified node
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if current.next is None:
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raise IndexError("Index out of range.")
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current = current.next
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return current
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# Used to change the data of a particular node
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def __setitem__(self, index, data):
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current = self.head
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# If list is empty
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if current is None:
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raise IndexError("The Linked List is empty")
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for i in range(index):
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if current.next is None:
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raise IndexError("Index out of range.")
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current = current.next
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current.data = data
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def __len__(self):
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def __len__(self) -> int:
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"""
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Return length of linked list i.e. number of nodes
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>>> linked_list = LinkedList()
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@ -126,45 +36,168 @@ class LinkedList:
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>>> len(linked_list)
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0
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"""
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if not self.head:
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return 0
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return len(tuple(iter(self)))
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count = 0
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cur_node = self.head
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while cur_node.next:
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count += 1
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cur_node = cur_node.next
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return count + 1
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def __repr__(self):
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"""
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String representation/visualization of a Linked Lists
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"""
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return "->".join([str(item) for item in self])
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def __getitem__(self, index):
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"""
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Indexing Support. Used to get a node at particular position
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"""
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if index < 0:
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raise ValueError("Negative indexes are not yet supported")
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for i, node in enumerate(self):
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if i == index:
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return node.data
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# Used to change the data of a particular node
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def __setitem__(self, index, data):
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current = self.head
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# If list is empty
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if current is None:
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raise IndexError("The Linked List is empty")
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for i in range(index):
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if current.next is None:
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raise IndexError("list index out of range")
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current = current.next
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current.data = data
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def insert_tail(self, data) -> None:
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self.insert_nth(len(self), data)
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def insert_head(self, data) -> None:
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self.insert_nth(0, data)
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def insert_nth(self, index: int, data) -> None:
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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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new_node = Node(data)
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if self.head is None:
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self.head = new_node
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elif index == 0:
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new_node.next = self.head # link new_node to head
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self.head = new_node
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else:
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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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def print_list(self) -> None: # print every node data
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print(self)
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def delete_head(self):
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return self.delete_nth(0)
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def delete_tail(self): # delete from tail
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return self.delete_nth(len(self) - 1)
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def delete_nth(self, index: int = 0):
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if not 0 <= index <= len(self) - 1: # test if index is valid
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raise IndexError("list index out of range")
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delete_node = self.head # default first node
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if index == 0:
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self.head = self.head.next
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else:
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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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return delete_node.data
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def is_empty(self) -> bool:
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return self.head is None
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def reverse(self):
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prev = None
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current = self.head
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while current:
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# Store the current node's next node.
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next_node = current.next
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# Make the current node's next point backwards
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current.next = prev
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# Make the previous node be the current node
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prev = current
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# Make the current node the next node (to progress iteration)
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current = next_node
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# Return prev in order to put the head at the end
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self.head = prev
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def test_singly_linked_list() -> None:
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"""
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>>> test_singly_linked_list()
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"""
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linked_list = LinkedList()
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assert linked_list.is_empty() is True
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assert str(linked_list) == ""
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try:
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linked_list.delete_head()
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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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try:
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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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for i in range(10):
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assert len(linked_list) == i
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linked_list.insert_nth(i, i + 1)
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assert str(linked_list) == "->".join(str(i) for i in range(1, 11))
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linked_list.insert_head(0)
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linked_list.insert_tail(11)
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assert str(linked_list) == "->".join(str(i) for i in range(0, 12))
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assert linked_list.delete_head() == 0
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assert linked_list.delete_nth(9) == 10
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assert linked_list.delete_tail() == 11
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assert str(linked_list) == "->".join(str(i) for i in range(1, 10))
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def main():
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A = LinkedList()
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A.insert_head(input("Inserting 1st at head ").strip())
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A.insert_head(input("Inserting 2nd at head ").strip())
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from doctest import testmod
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testmod()
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linked_list = LinkedList()
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linked_list.insert_head(input("Inserting 1st at head ").strip())
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linked_list.insert_head(input("Inserting 2nd at head ").strip())
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print("\nPrint list:")
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A.print_list()
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A.insert_tail(input("\nInserting 1st at tail ").strip())
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A.insert_tail(input("Inserting 2nd at tail ").strip())
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linked_list.print_list()
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linked_list.insert_tail(input("\nInserting 1st at tail ").strip())
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linked_list.insert_tail(input("Inserting 2nd at tail ").strip())
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print("\nPrint list:")
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A.print_list()
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linked_list.print_list()
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print("\nDelete head")
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A.delete_head()
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linked_list.delete_head()
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print("Delete tail")
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A.delete_tail()
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linked_list.delete_tail()
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print("\nPrint list:")
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A.print_list()
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linked_list.print_list()
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print("\nReverse linked list")
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A.reverse()
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linked_list.reverse()
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print("\nPrint list:")
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A.print_list()
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linked_list.print_list()
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print("\nString representation of linked list:")
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print(A)
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print(linked_list)
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print("\nReading/changing Node data using indexing:")
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print(f"Element at Position 1: {A[1]}")
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A[1] = input("Enter New Value: ").strip()
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print(f"Element at Position 1: {linked_list[1]}")
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linked_list[1] = input("Enter New Value: ").strip()
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print("New list:")
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print(A)
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print(f"length of A is : {len(A)}")
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print(linked_list)
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print(f"length of linked_list is : {len(linked_list)}")
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if __name__ == "__main__":
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