mirror of
https://github.com/donnemartin/interactive-coding-challenges.git
synced 2024-03-22 13:11:13 +08:00
Added notebook solving the following: Remove duplicates from a linked list.
This commit is contained in:
Donne Martin
parent
f652c7db1e
commit
1bfef18681
257
linked-lists/remove-duplicates.ipynb
Normal file
257
linked-lists/remove-duplicates.ipynb
Normal file
|
|
@ -0,0 +1,257 @@
|
|||
{
|
||||
"cells": [
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Problem: Remove duplicates from a linked list\n",
|
||||
"\n",
|
||||
"* [Clarifying Questions](#Clarifying-Questions)\n",
|
||||
"* [Test Cases](#Test-Cases)\n",
|
||||
"* [Algorithm: Hash Map Lookup](#Algorithm:-Hash-Map-Lookup)\n",
|
||||
"* [Code: Hash Map Lookup](#Code:-Hash-Map-Lookup)\n",
|
||||
"* [Algorithm: In-Place](#Algorithm:-In-Place)\n",
|
||||
"* [Code: In-Place](#Code:-In-Place)"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Clarifying Questions\n",
|
||||
"\n",
|
||||
"* Do we assume the linked list class already exists?\n",
|
||||
" * No, create one\n",
|
||||
"* Is this a singly or doubly linked list?\n",
|
||||
" * Singly\n",
|
||||
"* Can you insert NULL values in the list?\n",
|
||||
" * No\n",
|
||||
"* Can use additional data structures?\n",
|
||||
" * Implement both solutions"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Test Cases\n",
|
||||
"\n",
|
||||
"* Empty linked list\n",
|
||||
"* One element linked list\n",
|
||||
"* Multiple elements\n",
|
||||
"* No duplicates\n",
|
||||
"* One or more duplicates"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Algorithm: Hash Map Lookup\n",
|
||||
"\n",
|
||||
"* For each node\n",
|
||||
" * If the node's value is in the hash map\n",
|
||||
" * Delete the node\n",
|
||||
" * Else\n",
|
||||
" * Add node's value to the hash map\n",
|
||||
"\n",
|
||||
"Complexity:\n",
|
||||
"* Time: O(n)\n",
|
||||
"* Space: O(m) where m is the number of values in the hash map\n",
|
||||
"\n",
|
||||
"Note:\n",
|
||||
"* Deletion requires two pointers, one to the previous node and one to the current node"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Code: Hash Map Lookup"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "code",
|
||||
"execution_count": null,
|
||||
"metadata": {
|
||||
"collapsed": false
|
||||
},
|
||||
"outputs": [],
|
||||
"source": [
|
||||
"class Node(object):\n",
|
||||
" def __init__(self, data):\n",
|
||||
" self.next = None\n",
|
||||
" self.data = data\n",
|
||||
"\n",
|
||||
"class LinkedList(object):\n",
|
||||
" def __init__(self, head):\n",
|
||||
" self.head = head\n",
|
||||
" \n",
|
||||
" def remove_dupes(self):\n",
|
||||
" seen_data = set()\n",
|
||||
" curr = self.head\n",
|
||||
" prev = None\n",
|
||||
" while curr is not None:\n",
|
||||
" if curr.data in seen_data:\n",
|
||||
" prev.next = curr.next\n",
|
||||
" else:\n",
|
||||
" seen_data.add(curr.data)\n",
|
||||
" prev = curr\n",
|
||||
" curr = curr.next\n",
|
||||
" \n",
|
||||
" def insert_to_front(self, data):\n",
|
||||
" if data is None:\n",
|
||||
" return\n",
|
||||
" node = Node(data)\n",
|
||||
" if self.head is None:\n",
|
||||
" self.head = node\n",
|
||||
" else:\n",
|
||||
" node.next = self.head\n",
|
||||
" self.head = node \n",
|
||||
" \n",
|
||||
" def print_list(self):\n",
|
||||
" curr = self.head\n",
|
||||
" while curr is not None:\n",
|
||||
" print(curr.data)\n",
|
||||
" curr = curr.next\n",
|
||||
" \n",
|
||||
"# Empty linked list\n",
|
||||
"linked_list = LinkedList(None)\n",
|
||||
"linked_list.remove_dupes()\n",
|
||||
"linked_list.print_list()\n",
|
||||
"# One element linked list\n",
|
||||
"head = Node(2)\n",
|
||||
"linked_list = LinkedList(head)\n",
|
||||
"linked_list.remove_dupes()\n",
|
||||
"linked_list.print_list()\n",
|
||||
"# Multiple elements\n",
|
||||
"# One or more duplicates\n",
|
||||
"linked_list.insert_to_front(1)\n",
|
||||
"linked_list.insert_to_front(3)\n",
|
||||
"linked_list.insert_to_front(1)\n",
|
||||
"linked_list.insert_to_front(1)\n",
|
||||
"linked_list.remove_dupes()\n",
|
||||
"linked_list.print_list()\n",
|
||||
"# No duplicates\n",
|
||||
"linked_list.remove_dupes()\n",
|
||||
"linked_list.print_list()"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Algorithm: In-Place\n",
|
||||
"\n",
|
||||
"* For each node\n",
|
||||
" * Compare node with every other node\n",
|
||||
" * If the node's value is in the hash map\n",
|
||||
" * Delete the node\n",
|
||||
" * Else\n",
|
||||
" * Add node's value to the hash map\n",
|
||||
"\n",
|
||||
"Complexity:\n",
|
||||
"* Time: O(n^2)\n",
|
||||
"* Space: In-place\n",
|
||||
"\n",
|
||||
"Note:\n",
|
||||
"* Deletion requires two pointers, one to the previous node and one to the current node\n",
|
||||
"* We'll need to use a 'runner' to check every other node and compare it to the current node"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "markdown",
|
||||
"metadata": {},
|
||||
"source": [
|
||||
"## Code: In-Place"
|
||||
]
|
||||
},
|
||||
{
|
||||
"cell_type": "code",
|
||||
"execution_count": null,
|
||||
"metadata": {
|
||||
"collapsed": false
|
||||
},
|
||||
"outputs": [],
|
||||
"source": [
|
||||
"class Node(object):\n",
|
||||
" def __init__(self, data):\n",
|
||||
" self.next = None\n",
|
||||
" self.data = data\n",
|
||||
"\n",
|
||||
"class LinkedList(object):\n",
|
||||
" def __init__(self, head):\n",
|
||||
" self.head = head\n",
|
||||
" \n",
|
||||
" def remove_dupes(self):\n",
|
||||
" curr = self.head\n",
|
||||
" while curr is not None:\n",
|
||||
" runner = curr\n",
|
||||
" while runner.next is not None:\n",
|
||||
" if runner.next.data == curr.data:\n",
|
||||
" runner.next = runner.next.next\n",
|
||||
" else:\n",
|
||||
" runner = runner.next\n",
|
||||
" curr = curr.next\n",
|
||||
" \n",
|
||||
" def insert_to_front(self, data):\n",
|
||||
" if data is None:\n",
|
||||
" return\n",
|
||||
" node = Node(data)\n",
|
||||
" if self.head is None:\n",
|
||||
" self.head = node\n",
|
||||
" else:\n",
|
||||
" node.next = self.head\n",
|
||||
" self.head = node \n",
|
||||
" \n",
|
||||
" def print_list(self):\n",
|
||||
" curr = self.head\n",
|
||||
" while curr is not None:\n",
|
||||
" print(curr.data)\n",
|
||||
" curr = curr.next\n",
|
||||
" \n",
|
||||
"# Empty linked list\n",
|
||||
"linked_list = LinkedList(None)\n",
|
||||
"linked_list.remove_dupes()\n",
|
||||
"linked_list.print_list()\n",
|
||||
"# One element linked list\n",
|
||||
"head = Node(2)\n",
|
||||
"linked_list = LinkedList(head)\n",
|
||||
"linked_list.remove_dupes()\n",
|
||||
"linked_list.print_list()\n",
|
||||
"# Multiple elements\n",
|
||||
"# One or more duplicates\n",
|
||||
"linked_list.insert_to_front(1)\n",
|
||||
"linked_list.insert_to_front(3)\n",
|
||||
"linked_list.insert_to_front(1)\n",
|
||||
"linked_list.insert_to_front(1)\n",
|
||||
"linked_list.remove_dupes()\n",
|
||||
"linked_list.print_list()\n",
|
||||
"# No duplicates\n",
|
||||
"linked_list.remove_dupes()\n",
|
||||
"linked_list.print_list()"
|
||||
]
|
||||
}
|
||||
],
|
||||
"metadata": {
|
||||
"kernelspec": {
|
||||
"display_name": "Python 2",
|
||||
"language": "python",
|
||||
"name": "python2"
|
||||
},
|
||||
"language_info": {
|
||||
"codemirror_mode": {
|
||||
"name": "ipython",
|
||||
"version": 2
|
||||
},
|
||||
"file_extension": ".py",
|
||||
"mimetype": "text/x-python",
|
||||
"name": "python",
|
||||
"nbconvert_exporter": "python",
|
||||
"pygments_lexer": "ipython2",
|
||||
"version": "2.7.9"
|
||||
}
|
||||
},
|
||||
"nbformat": 4,
|
||||
"nbformat_minor": 0
|
||||
}
|
||||
Loading…
Reference in New Issue
Block a user