mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
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420 lines
11 KiB
Plaintext
420 lines
11 KiB
Plaintext
{
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"cells": [
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"<small><i>This notebook was prepared by [Donne Martin](http://donnemartin.com). Source and license info is on [GitHub](https://bit.ly/code-notes).</i></small>"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Problem: Implement a linked list with insert, append, find, delete, length, and print methods\n",
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"\n",
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"* [Clarifying Questions](#Clarifying-Questions)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Clarifying Questions\n",
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"\n",
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"* Is this a singly or doubly linked list?\n",
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" * Singly\n",
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"* Is this a circular list?\n",
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" * No\n",
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"* Do we keep track of the tail or just the head?\n",
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" * Just the head"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Test Cases\n",
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"\n",
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"### Insert to Front\n",
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"\n",
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"* Insert a NULL\n",
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"* Insert in an empty list\n",
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"* Insert in a list with one element or more elements\n",
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"\n",
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"### Append\n",
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"\n",
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"* Append a NULL\n",
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"* Append in an empty list\n",
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"* Insert in a list with one element or more elements\n",
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"\n",
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"### Find\n",
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"\n",
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"* Find a NULL\n",
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"* Find in an empty list\n",
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"* Find in a list with one element or more matching elements\n",
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"* Find in a list with no matches\n",
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"\n",
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"### Delete\n",
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"\n",
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"* Delete a NULL\n",
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"* Delete in an empty list\n",
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"* Delete in a list with one element or more matching elements\n",
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"* Delete in a list with no matches\n",
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"\n",
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"### Length\n",
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"\n",
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"* Length of zero or more elements\n",
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"\n",
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"### Print\n",
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"\n",
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"* Print an empty list\n",
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"* Print a list with one or more elements"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Algorithm\n",
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"\n",
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"### Insert to Front\n",
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"\n",
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"* If the data we are inserting is NULL, return\n",
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"* Create a node with the input data\n",
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"* If this is an empty list\n",
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" * Assign the head to the node\n",
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"* Else\n",
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" * Set the node.next to the head\n",
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" * Set the head to the node\n",
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"\n",
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"Complexity:\n",
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"* Time: O(1)\n",
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"* Space: O(1), a new node is added\n",
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"\n",
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"### Append\n",
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"\n",
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"* If the data we are inserting is NULL, return\n",
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"* Create a node with the input data\n",
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"* If this is an empty list\n",
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" * Assign the head to the node\n",
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"* Else\n",
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" * Iterate to the end of the list\n",
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" * Set the final node's next to the new node\n",
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"\n",
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"Complexity:\n",
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"* Time: O(n)\n",
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"* Space: O(1), a new node is added\n",
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"\n",
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"### Find\n",
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"\n",
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"* If data we are finding is NULL, return\n",
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"* If the list is empty, return\n",
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"* For each node\n",
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" * If the value is a match, return it\n",
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" * Else, move on to the next node\n",
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"\n",
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"Complexity:\n",
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"* Time: O(n)\n",
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"* Space: In-place\n",
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"\n",
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"### Delete\n",
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"\n",
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"* If data we are deleting is NULL, return\n",
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"* If the list is empty, return\n",
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"* For each node, keep track of previous and current node\n",
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" * If the value we are deleting is a match in the current node\n",
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" * Update previous node's next pointer to the current node's next pointer\n",
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" * We do not have have to explicitly delete in Python\n",
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" * Else, move on to the next node\n",
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"\n",
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"Complexity:\n",
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"* Time: O(n)\n",
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"* Space: In-place\n",
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"\n",
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"### Length\n",
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"\n",
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"* For each node\n",
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" * Increase length counter\n",
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" \n",
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"Complexity:\n",
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"* Time: O(n)\n",
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"* Space: In-place\n",
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"\n",
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"### Print\n",
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"\n",
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"* For each node\n",
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" * Print the node's value\n",
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" \n",
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"Complexity:\n",
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"* Time: O(n)\n",
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"* Space: In-place"
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]
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},
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{
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"cell_type": "markdown",
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"metadata": {},
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"source": [
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"## Code"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"%%writefile linked_list.py\n",
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"\n",
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"class Node(object):\n",
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" def __init__(self, data, next_node=None):\n",
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" self.next = next_node\n",
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" self.data = data\n",
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" \n",
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" def __str__(self):\n",
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" return self.data\n",
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"\n",
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"class LinkedList(object):\n",
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" def __init__(self, head=None):\n",
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" self.head = head\n",
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"\n",
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" def __len__(self):\n",
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" curr = self.head\n",
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" counter = 0\n",
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" while curr is not None:\n",
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" counter += 1\n",
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" curr = curr.next\n",
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" return counter\n",
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" \n",
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" def insert_to_front(self, data):\n",
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" if data is None:\n",
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" return\n",
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" node = Node(data)\n",
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" if self.head is None:\n",
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" self.head = node\n",
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" else:\n",
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" node.next = self.head\n",
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" self.head = node\n",
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" \n",
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" def append(self, data, next_node=None):\n",
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" if data is None:\n",
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" return\n",
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" node = Node(data, next_node)\n",
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" if self.head is None:\n",
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" self.head = node\n",
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" else:\n",
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" curr_node = self.head\n",
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" while curr_node.next is not None:\n",
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" curr_node = curr_node.next\n",
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" curr_node.next = node\n",
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" \n",
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" def find(self, data):\n",
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" if data is None:\n",
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" return\n",
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" if self.head is None:\n",
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" return\n",
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" curr_node = self.head\n",
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" while curr_node is not None:\n",
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" if curr_node.data == data:\n",
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" return curr_node\n",
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" else:\n",
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" curr_node = curr_node.next\n",
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" \n",
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" def delete(self, data):\n",
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" if data is None:\n",
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" return\n",
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" if self.head is None:\n",
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" return\n",
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" prev_node = self.head\n",
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" curr_node = prev_node.next\n",
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" while curr_node is not None:\n",
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" if curr_node.data == data:\n",
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" prev_node.next = curr_node.next\n",
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" return\n",
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" else:\n",
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" prev_node = curr_node\n",
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" curr_node = curr_node.next\n",
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"\n",
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" def print_list(self):\n",
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" curr_node = self.head\n",
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" while curr_node is not None:\n",
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" print(curr_node.data)\n",
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" curr_node = curr_node.next"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": true
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},
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"outputs": [],
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"source": [
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"%run linked_list.py"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# Test insert_to_front\n",
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"# Insert in an empty list\n",
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"linked_list = LinkedList(None)\n",
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"linked_list.insert_to_front(10)\n",
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"linked_list.print_list()\n",
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"# Insert a NULL\n",
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"linked_list.insert_to_front(None)\n",
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"linked_list.print_list()\n",
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"# Insert in a list with one element or more elements\n",
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"linked_list.insert_to_front('a')\n",
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"linked_list.insert_to_front('bc')\n",
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"linked_list.print_list()"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# Test append\n",
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"# Insert in an empty list\n",
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"linked_list = LinkedList(None)\n",
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"linked_list.append(10)\n",
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"linked_list.print_list()\n",
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"# Insert a NULL\n",
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"linked_list.append(None)\n",
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"linked_list.print_list()\n",
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"# Insert in a list with one element or more elements\n",
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"linked_list.append('a')\n",
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"linked_list.append('bc')\n",
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"linked_list.print_list()"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# Test find\n",
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"# Find in an empty list\n",
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"linked_list = LinkedList(None)\n",
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"node = linked_list.find('a')\n",
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"print(node)\n",
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"# Find a NULL\n",
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"head = Node(10)\n",
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"linked_list = LinkedList(head)\n",
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"node = linked_list.find(None)\n",
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"print(node)\n",
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"# Find in a list with one element or more matching elements\n",
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"head = Node(10)\n",
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"linked_list = LinkedList(head)\n",
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"linked_list.insert_to_front('a')\n",
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"linked_list.insert_to_front('bc')\n",
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"node = linked_list.find('a')\n",
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"print(node)\n",
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"# Find in a list with no matches\n",
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"node = linked_list.find('aaa')\n",
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"print(node)"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# Test delete\n",
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"# Delete in an empty list\n",
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"linked_list = LinkedList(None)\n",
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"linked_list.delete('a')\n",
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"linked_list.print_list()\n",
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"# Delete a NULL\n",
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"head = Node(10)\n",
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"linked_list = LinkedList(head)\n",
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"linked_list.delete(None)\n",
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"linked_list.print_list()\n",
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"# Delete in a list with one element or more matching elements\n",
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"head = Node(10)\n",
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"linked_list = LinkedList(head)\n",
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"linked_list.insert_to_front('a')\n",
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"linked_list.insert_to_front('bc')\n",
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"linked_list.delete('a')\n",
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"linked_list.print_list()\n",
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"# Delete in a list with no matches\n",
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"linked_list.delete('aa')"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# Test length\n",
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"# Zero elements\n",
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"linked_list = LinkedList(None)\n",
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"print(len(linked_list))\n",
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"# One or more elements\n",
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"head = Node(10)\n",
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"linked_list = LinkedList(head)\n",
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"linked_list.insert_to_front('a')\n",
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"linked_list.insert_to_front('bc')\n",
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"print(len(linked_list))"
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]
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},
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{
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"cell_type": "code",
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"execution_count": null,
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"metadata": {
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"collapsed": false
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},
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"outputs": [],
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"source": [
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"# Test empty print\n",
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"linked_list = LinkedList(None)\n",
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"linked_list.print_list()"
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]
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}
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],
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"metadata": {
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"kernelspec": {
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"display_name": "Python 2",
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"language": "python",
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"name": "python2"
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},
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"language_info": {
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"codemirror_mode": {
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"name": "ipython",
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"version": 2
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},
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"file_extension": ".py",
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"mimetype": "text/x-python",
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"name": "python",
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"nbconvert_exporter": "python",
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"pygments_lexer": "ipython2",
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"version": "2.7.10"
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}
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},
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"nbformat": 4,
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"nbformat_minor": 0
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}
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