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| class LinkedList(): | |
| """A singly general purpose linked list implementation.""" | |
| class _Node(): | |
| """A singly linked node.""" | |
| def __init__(self, value, next=None): | |
| self.next = next | |
| self.value = value | |
| @property | |
| def has_next(self): | |
| return this.next is None | |
| def __repr__(self): | |
| return f'({self.value} -> {self.next and self.next.value})' | |
| def __str__(self): | |
| return self.__repr__() | |
| class _LinkedListIterator(): | |
| """An iterator for the singly linked list.""" | |
| def __init__(self, linked_list): | |
| self._linked_list = linked_list | |
| self._current = None | |
| def __iter__(self): | |
| return self | |
| def __next__(self): | |
| if self._current is None: | |
| self._current = self._linked_list._head | |
| else: | |
| self._current = self._current.next | |
| if self._current is None: | |
| raise StopIteration() | |
| return self._current.value | |
| def __init__(self, *initial_values): | |
| self._head = None | |
| self._tail = None | |
| self._size = 0 | |
| self._next = None | |
| for e in reversed(initial_values): | |
| self.prepend(e) | |
| def __len__(self): | |
| return self._size | |
| @property | |
| def is_empty(self): | |
| """Whether the list is empty or not.""" | |
| return self._size == 0 | |
| def prepend(self, e): | |
| """Links an element to the head of the list.""" | |
| self._head = self._Node(e, self._head) | |
| if self.is_empty: | |
| self._tail = self._head | |
| self._size += 1 | |
| def append(self, e): | |
| """Links an element to the tail of the list.""" | |
| new_node = self._Node(e) | |
| if self.is_empty: | |
| self._tail = new_node | |
| self._head = self._tail | |
| else: | |
| self._tail.next = new_node | |
| self._tail = self._tail.next | |
| self._size += 1 | |
| def map(self, fn): | |
| """Maps a function to all values in the list, returning a new list.""" | |
| return LinkedList(*map(fn, self)) | |
| def __iter__(self): | |
| return self._LinkedListIterator(self) | |
| def __repr__(self): | |
| return f'LinkedList({self.__str__()})' | |
| def __str__(self): | |
| return ', '.join(map(repr, self)) | |
| def __getitem__(self, index): | |
| if self.is_empty or index >= self._size or index < 0: | |
| raise IndexError(f'LinkedList(size={self._size}) has no index {index}') | |
| self_iter = iter(self) | |
| for _ in range(0, index + 1): | |
| cur = next(self_iter) | |
| return cur |
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