mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
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473 lines
14 KiB
Plaintext
473 lines
14 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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"* [Constraints and Assumptions](#Constraints-and-Assumptions)\n",
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"* [Test Cases](#Test-Cases)\n",
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"* [Algorithm](#Algorithm)\n",
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"* [Code](#Code)\n",
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"* [Unit Test](#Unit-Test)"
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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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"## Constraints and Assumptions\n",
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"\n",
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"*Problem statements are often intentionally ambiguous. Identifying constraints and stating assumptions can help to ensure you code the intended solution.*\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": 1,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Overwriting linked_list.py\n"
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]
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}
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],
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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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" return 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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" return 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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" return\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\n",
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"\n",
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" def get_all_data(self):\n",
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" data = []\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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" data.append(curr_node.data)\n",
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" curr_node = curr_node.next\n",
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" return data"
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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": 2,
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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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"%run linked_list.py"
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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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"## Unit Test"
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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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"*It is important to identify and run through general and edge cases from the [Test Cases](#Test-Cases) section by hand. You generally will not be asked to write a unit test like what is shown below.*"
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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": 3,
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"metadata": {
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"collapsed": false
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},
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"outputs": [
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{
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"name": "stdout",
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"output_type": "stream",
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"text": [
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"Test: insert_to_front on an empty list\n",
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"Test: insert_to_front on a NULL\n",
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"Test: insert_to_front general case\n",
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"Success: test_insert_to_front\n",
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"\n",
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"Test: append on an empty list\n",
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"Test: append a NULL\n",
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"Test: append general case\n",
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"Success: test_append\n",
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"\n",
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"Test: find on an empty list\n",
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"Test: find a NULL\n",
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"Test: find general case with matches\n",
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"Test: find general case with no matches\n",
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"Success: test_find\n",
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"\n",
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"Test: delete on an empty list\n",
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"Test: delete a NULL\n",
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"Test: delete general case with matches\n",
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"Test: delete general case with no matches\n",
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"Success: test_delete\n",
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"\n",
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"Test: len on an empty list\n",
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"Test: len general case\n",
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"Success: test_len\n",
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"\n"
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]
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}
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],
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"source": [
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"from nose.tools import assert_equal\n",
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"\n",
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"class Test(object):\n",
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" def test_insert_to_front(self):\n",
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" print('Test: insert_to_front on 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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" assert_equal(linked_list.get_all_data(), [10])\n",
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"\n",
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" print('Test: insert_to_front on a NULL')\n",
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" linked_list.insert_to_front(None)\n",
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" assert_equal(linked_list.get_all_data(), [10])\n",
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"\n",
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" print('Test: insert_to_front general case')\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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" assert_equal(linked_list.get_all_data(), ['bc', 'a', 10])\n",
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" \n",
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" print('Success: test_insert_to_front\\n')\n",
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" \n",
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" def test_append(self):\n",
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" print('Test: append on 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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" assert_equal(linked_list.get_all_data(), [10])\n",
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"\n",
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" print('Test: append a NULL')\n",
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" linked_list.append(None)\n",
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" assert_equal(linked_list.get_all_data(), [10])\n",
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"\n",
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" print('Test: append general case')\n",
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" linked_list.append('a')\n",
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" linked_list.append('bc')\n",
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" assert_equal(linked_list.get_all_data(), [10, 'a', 'bc'])\n",
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" \n",
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" print('Success: test_append\\n')\n",
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" \n",
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" def test_find(self):\n",
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" print('Test: find on 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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" assert_equal(node, None)\n",
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"\n",
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" print('Test: 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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" assert_equal(node, None)\n",
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"\n",
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" print('Test: find general case with matches')\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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" assert_equal(str(node), 'a')\n",
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"\n",
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" print('Test: find general case with no matches')\n",
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" node = linked_list.find('aaa')\n",
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" assert_equal(node, None)\n",
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" \n",
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" print('Success: test_find\\n')\n",
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" \n",
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" def test_delete(self):\n",
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" print('Test: delete on 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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" assert_equal(linked_list.get_all_data(), [])\n",
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"\n",
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" print('Test: 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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" assert_equal(linked_list.get_all_data(), [10])\n",
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"\n",
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" print('Test: delete general case with matches')\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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" assert_equal(linked_list.get_all_data(), ['bc', 10])\n",
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"\n",
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" print('Test: delete general case with no matches')\n",
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" linked_list.delete('aa')\n",
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" assert_equal(linked_list.get_all_data(), ['bc', 10])\n",
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" \n",
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" print('Success: test_delete\\n')\n",
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" \n",
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" def test_len(self):\n",
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" print('Test: len on an empty list')\n",
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" linked_list = LinkedList(None)\n",
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" assert_equal(len(linked_list), 0)\n",
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"\n",
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" print('Test: len general case')\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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" assert_equal(len(linked_list), 3)\n",
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" \n",
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" print('Success: test_len\\n')\n",
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"\n",
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"if __name__ == '__main__':\n",
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" test = Test()\n",
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" test.test_insert_to_front()\n",
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" test.test_append()\n",
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" test.test_find()\n",
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" test.test_delete()\n",
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" test.test_len()"
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]
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}
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],
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"metadata": {
|
|
"kernelspec": {
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"display_name": "Python 2",
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|
"language": "python",
|
|
"name": "python2"
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|
},
|
|
"language_info": {
|
|
"codemirror_mode": {
|
|
"name": "ipython",
|
|
"version": 2
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},
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|
"file_extension": ".py",
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|
"mimetype": "text/x-python",
|
|
"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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|
}
|