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[chore] update readme, replace py file with notebook
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,195 @@ | ||
| { | ||
| "metadata": { | ||
| "language_info": { | ||
| "codemirror_mode": { | ||
| "name": "ipython", | ||
| "version": 3 | ||
| }, | ||
| "file_extension": ".py", | ||
| "mimetype": "text/x-python", | ||
| "name": "python", | ||
| "nbconvert_exporter": "python", | ||
| "pygments_lexer": "ipython3", | ||
| "version": "3.9.0-final" | ||
| }, | ||
| "orig_nbformat": 2, | ||
| "kernelspec": { | ||
| "name": "python3", | ||
| "display_name": "Python 3.9.0 64-bit", | ||
| "metadata": { | ||
| "interpreter": { | ||
| "hash": "aee8b7b246df8f9039afb4144a1f6fd8d2ca17a180786b69acc140d282b71a49" | ||
| } | ||
| } | ||
| } | ||
| }, | ||
| "nbformat": 4, | ||
| "nbformat_minor": 2, | ||
| "cells": [ | ||
| { | ||
| "cell_type": "code", | ||
| "execution_count": 3, | ||
| "metadata": {}, | ||
| "outputs": [], | ||
| "source": [ | ||
| "class Node:\n", | ||
| " def __init__(self, value):\n", | ||
| " self.value = value\n", | ||
| " self.prev = None\n", | ||
| " self.next = None\n", | ||
| "\n", | ||
| "\n", | ||
| "class DoubleLinkedList:\n", | ||
| " def __init__(self):\n", | ||
| " self.head = None\n", | ||
| " self.tail = None\n", | ||
| "\n", | ||
| " def set_head(self, node):\n", | ||
| " \"\"\"O(1) time | O(1) space\"\"\"\n", | ||
| " if self.head is None:\n", | ||
| " self.head = node\n", | ||
| " self.tail = node\n", | ||
| " return\n", | ||
| " self.insert_before(self.head, node)\n", | ||
| "\n", | ||
| " def set_tail(self, node):\n", | ||
| " \"\"\"O(1) time | O(1) space\"\"\"\n", | ||
| " if self.tail is None:\n", | ||
| " self.set_head(node)\n", | ||
| " return\n", | ||
| " self.insert_after(self.tail, node)\n", | ||
| "\n", | ||
| " def insert_before(self, node, node_to_insert):\n", | ||
| " \"\"\"O(1) time | O(1) space\"\"\"\n", | ||
| " if node_to_insert == self.head and node_to_insert == self.tail:\n", | ||
| " return\n", | ||
| " # first, remove node if it exists\n", | ||
| " self.remove(node_to_insert)\n", | ||
| " node_to_insert.prev = node.prev\n", | ||
| " node_to_insert.next = node\n", | ||
| "\n", | ||
| " if node.prev is None:\n", | ||
| " self.head = node_to_insert\n", | ||
| " else:\n", | ||
| " node.prev.next = node_to_insert\n", | ||
| " node.prev = node_to_insert\n", | ||
| "\n", | ||
| " def insert_after(self, node, node_to_insert):\n", | ||
| " \"\"\"O(1) time | O(1) space\"\"\"\n", | ||
| " if node_to_insert == self.head and node_to_insert == self.tail:\n", | ||
| " return\n", | ||
| " # first remove the node to insert if it currently exists in the linked list\n", | ||
| " self.remove(node_to_insert)\n", | ||
| " node_to_insert.prev = node\n", | ||
| " node_to_insert.next = node.next\n", | ||
| "\n", | ||
| " if node.next is None:\n", | ||
| " self.tail = node_to_insert\n", | ||
| " else:\n", | ||
| " node.prev.next = node_to_insert\n", | ||
| " node.next = node_to_insert\n", | ||
| "\n", | ||
| " def insert_at_position(self, position, node_to_insert):\n", | ||
| " \"\"\"O(1) space | O(p) time - since we are iterating up until position p\"\"\"\n", | ||
| " if position == 1:\n", | ||
| " self.set_head(node_to_insert)\n", | ||
| " return\n", | ||
| " node = self.head\n", | ||
| " current_position = 1\n", | ||
| " while node is not None and current_position != position:\n", | ||
| " node = node.next\n", | ||
| " current_position += 1\n", | ||
| " if node is not None:\n", | ||
| " self.insert_before(node, node_to_insert)\n", | ||
| " else:\n", | ||
| " # node is None so we are at the tail\n", | ||
| " self.set_tail(node_to_insert)\n", | ||
| "\n", | ||
| " def remove_nodes_with_value(self, value):\n", | ||
| " \"\"\"O(n) time | O(1) space\"\"\"\n", | ||
| " node = self.head\n", | ||
| " while node is not None:\n", | ||
| " # temporary save the current node, to not lose it while we check\n", | ||
| " # if it needs to be removed\n", | ||
| " node_to_remove = node\n", | ||
| " # update the node to be the next node\n", | ||
| " node = node.next\n", | ||
| " if node_to_remove.value == value:\n", | ||
| " self.remove(node_to_remove)\n", | ||
| "\n", | ||
| " def remove(self, node):\n", | ||
| " \"\"\"O(1) time | O(1) space\"\"\"\n", | ||
| " if node == self.head:\n", | ||
| " self.head = self.head.next\n", | ||
| " if node == self.tail:\n", | ||
| " self.tail = self.tail.prev\n", | ||
| " self.update_node_bindings(node)\n", | ||
| "\n", | ||
| " def contains_node_with_value(self, value):\n", | ||
| " \"\"\"O(n) time | O(1) space\"\"\"\n", | ||
| " node = self.head\n", | ||
| " while node is not None and node.value != value:\n", | ||
| " node = node.next\n", | ||
| " return node is not None\n", | ||
| "\n", | ||
| " def update_node_bindings(self, node):\n", | ||
| " \"\"\"Update the pointers of a node when a node is removed from the doubly linked list.\n", | ||
| " \"\"\"\n", | ||
| " # the order in which you remove pointers matters. otherwise, we might delete nodes\n", | ||
| " # and never recover them forever.\n", | ||
| " if node.prev is not None:\n", | ||
| " node.prev.next = node.next\n", | ||
| " if node.next is not None:\n", | ||
| " node.next.prev = node.prev\n", | ||
| " node.prev = None\n", | ||
| " node.next = None" | ||
| ] | ||
| }, | ||
| { | ||
| "cell_type": "code", | ||
| "execution_count": 4, | ||
| "metadata": {}, | ||
| "outputs": [], | ||
| "source": [ | ||
| "\n", | ||
| "doubly_linked_list = DoubleLinkedList()\n", | ||
| "first_node = Node(1)\n", | ||
| "second_node = Node(2)\n", | ||
| "third_node = Node(3)\n", | ||
| "\n", | ||
| "doubly_linked_list.set_head(first_node)\n", | ||
| "doubly_linked_list.set_tail(third_node)\n", | ||
| "doubly_linked_list.insert_before(third_node, second_node)\n", | ||
| "another_node = Node(7)\n", | ||
| "doubly_linked_list.insert_after(third_node, another_node)\n" | ||
| ] | ||
| }, | ||
| { | ||
| "cell_type": "code", | ||
| "execution_count": 5, | ||
| "metadata": {}, | ||
| "outputs": [ | ||
| { | ||
| "output_type": "execute_result", | ||
| "data": { | ||
| "text/plain": [ | ||
| "1" | ||
| ] | ||
| }, | ||
| "metadata": {}, | ||
| "execution_count": 5 | ||
| } | ||
| ], | ||
| "source": [ | ||
| "doubly_linked_list.head.value" | ||
| ] | ||
| }, | ||
| { | ||
| "cell_type": "code", | ||
| "execution_count": null, | ||
| "metadata": {}, | ||
| "outputs": [], | ||
| "source": [] | ||
| } | ||
| ] | ||
| } |
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