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Simple implementation of Linked List in python
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| class Node: | |
| def __init__(self, value, prev=None, next=None): | |
| self.value = value | |
| self.prev = prev | |
| self.next = next | |
| def __repr__(self): | |
| return f"Node({self.value})" | |
| class LinkedList: | |
| def __init__(self, *values): | |
| self.head = None | |
| self.tail = None | |
| self.size = 0 | |
| for value in values: | |
| self.push_back(value) | |
| def __len__(self): | |
| return self.size | |
| def __str__(self): | |
| result = '[' | |
| if self.head: | |
| result += str(self.head.value) | |
| node = self.head | |
| while node.next: | |
| node = node.next | |
| result += ", " + str(node.value) | |
| result += ']' | |
| return result | |
| def is_empty(self): | |
| return self.size == 0 | |
| def push_back(self, value): | |
| new_node = Node(value) | |
| if self.tail is None: | |
| self.head = new_node | |
| self.tail = new_node | |
| else: | |
| self.tail.next = new_node | |
| new_node.prev = self.tail | |
| self.tail = new_node | |
| self.size += 1 | |
| def push_front(self, value): | |
| new_node = Node(value) | |
| if self.head is None: | |
| self.head = new_node | |
| self.tail = new_node | |
| else: | |
| self.head.prev = new_node | |
| new_node.next = self.head | |
| self.head = new_node | |
| self.size += 1 | |
| def pop_back(self): | |
| if self.tail is None: | |
| return | |
| value = self.tail.value | |
| self.tail = self.tail.prev | |
| if self.tail is None: | |
| self.head = None | |
| else: | |
| self.tail.next = None | |
| self.size -= 1 | |
| return value | |
| def pop_front(self): | |
| if self.head is None: | |
| return | |
| value = self.head.value | |
| self.head = self.head.next | |
| if self.head is None: | |
| self.tail = None | |
| else: | |
| self.head.prev = None | |
| self.size -= 1 | |
| return value | |
| def peek_back(self): | |
| if self.tail: | |
| return self.tail.value | |
| def peek_front(self): | |
| if self.head: | |
| return self.head.value | |
| def find(self, value): | |
| if self.head: | |
| index = 0 | |
| node = self.head | |
| while node: | |
| if node.value == value: | |
| return index | |
| node = node.next | |
| index += 1 | |
| def get_from_left(self, index): | |
| i = 0 | |
| node = self.head | |
| result = node | |
| while node and i < index: | |
| result = node | |
| node = node.next | |
| i += 1 | |
| return result | |
| def get_from_right(self, index): | |
| i = self.size | |
| node = self.tail | |
| result = node | |
| while node and i > index: | |
| result = node | |
| node = node.prev | |
| i -= 1 | |
| return result | |
| def get_node(self, index): | |
| if index < 0: | |
| index = self.size + index | |
| if index >= self.size: | |
| raise IndexError | |
| if index + 1 > self.size / 2: | |
| return self.get_from_right(index) | |
| return self.get_from_left(index) | |
| def pop_at(self, index): | |
| node = self.get_node(index) | |
| if node is self.head: | |
| return self.pop_front() | |
| if node is self.tail: | |
| return self.pop_back() | |
| value = None | |
| if node and node.prev and node.next: | |
| node.prev.next = node.next | |
| node.next.prev = node.prev | |
| value = node.value | |
| node = None | |
| self.size -= 1 | |
| return value | |
| def extend(self, other): | |
| if self.tail is None: | |
| self.head = other.head | |
| self.tail = other.tail | |
| else: | |
| self.tail.next = other.head | |
| self.tail = other.tail | |
| self.size += other.size | |
| def test(): | |
| first_list = LinkedList() | |
| first_list.push_back(69) | |
| first_list.push_back(420) | |
| first_list.push_back(4) | |
| first_list.push_front(4) | |
| print(first_list) | |
| print(first_list.pop_front()) | |
| print(first_list) | |
| print(first_list.pop_back()) | |
| print(first_list) | |
| second_list = LinkedList(6, 9, 4, 2, 0) | |
| first_list.extend(second_list) | |
| print(first_list) | |
| print(first_list.pop_at(5)) | |
| print(first_list.pop_at(-4)) | |
| print(first_list) | |
| print(first_list.find(9)) | |
| print(len(first_list)) | |
| if __name__ == "__main__": | |
| test() |
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