148 lines
4.1 KiB
Python
148 lines
4.1 KiB
Python
"""
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1) Insertion, deletion and search of singly-linked list;
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2) Assumes int type for data in list nodes.
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Author: Wenru
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"""
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from typing import Optional
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class Node:
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def __init__(self, data: int, next_node=None):
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self.data = data
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self._next = next_node
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class SinglyLinkedList:
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def __init__(self):
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self._head = None
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def find_by_value(self, value: int) -> Optional[Node]:
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p = self._head
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while p and p.data != value:
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p = p._next
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return p
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def find_by_index(self, index: int) -> Optional[Node]:
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p = self._head
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position = 0
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while p and position != index:
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p = p._next
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position += 1
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return p
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def insert_value_to_head(self, value: int):
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new_node = Node(value)
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self.insert_node_to_head(new_node)
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def insert_node_to_head(self, new_node: Node):
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if new_node:
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new_node._next = self._head
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self._head = new_node
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def insert_value_after(self, node: Node, value: int):
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new_node = Node(value)
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self.insert_node_after(node, new_node)
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def insert_node_after(self, node: Node, new_node: Node):
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if not node or not new_node:
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return
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new_node._next = node._next
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node._next = new_node
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def insert_value_before(self, node: Node, value: int):
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new_node = Node(value)
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self.insert_node_before(node, new_node)
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def insert_node_before(self, node: Node, new_node: Node):
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if not self._head or not node or not new_node:
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return
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if self._head == node:
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self.insert_node_to_head(new_node)
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return
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current = self._head
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while current._next and current._next != node:
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current = current._next
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if not current._next: # node is not even in the list
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return
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new_node._next = node
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current._next = new_node
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def delete_by_node(self, node: Node):
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if not self._head or not node:
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return
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if node._next:
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node.data = node._next.data
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node._next = node._next._next
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return
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# node is the last one or not in the list
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current = self._head
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while current and current._next != node:
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current = current._next
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if not current: # node not in the list
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return
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current._next = node._next
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def delete_by_value(self, value: int):
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if not self._head or not value:
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return
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fake_head = Node(value + 1)
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fake_head._next = self._head
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prev, current = fake_head, self._head
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while current:
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if current.data != value:
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prev._next = current
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prev = prev._next
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current = current._next
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if prev._next:
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prev._next = None
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self._head = fake_head._next # in case head.data == value
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def __repr__(self) -> str:
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nums = []
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current = self._head
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while current:
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nums.append(current.data)
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current = current._next
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if len(nums) > 0:
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return "->".join(str(num) for num in nums)
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else:
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return ""
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# 重写__iter__方法，方便for关键字调用打印值
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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 print_all(self):
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current = self._head
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if current:
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print(f"{current.data}", end="")
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current = current._next
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while current:
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print(f"->{current.data}", end="")
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current = current._next
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print("\n", flush=True)
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if __name__ == "__main__":
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l = SinglyLinkedList()
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for i in range(15):
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l.insert_value_to_head(i)
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node9 = l.find_by_value(9)
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l.insert_value_before(node9, 20)
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l.insert_value_before(node9, 16)
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l.insert_value_before(node9, 16)
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l.delete_by_value(16)
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node11 = l.find_by_index(3)
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l.delete_by_node(node11)
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l.delete_by_node(l._head)
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l.delete_by_value(13)
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print(l)
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for value in l:
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print(value)
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