Advent of code
For the joy of finding things out, I thought I’d try AoC
Other challenges like Project Euler are here
JavaScript / TypeScript
I’ve never really tried out the JS/TS world, so this is an opportunity.
Install notes on React helped on my laptop.
# https://github.com/nvm-sh/nvm
curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.1/install.sh | bash
# 0.40.1 on 4th Nov 24
nvm --version
# Node.js (LTS) if 22.11.0 on 4th Nov 24
nvm install --lts
npm --version
npm install -g typescript
# 5.7.2 on 2nd Dev 2024
tsc -v
# run TS on Node without precompile
npm install -g tsx --verbose
Hello World
# compiles to app.js
tsc app.ts
# runs the js
node app.js
and
let message: string = 'Hello, World!';
console.log(message);
which compiles to
var message = 'Hello, World!';
console.log(message);
Why TS?
TypeScript is a superset of JavaScript that compiles to plain JavaScript
- TypeScript adds a type system to help you avoid many problems with dynamic types in JavaScript.
- TypeScript implements the future features of JavaScript a.k.a ES Next so you can use them today.
VSCode
How do I setup VSCode to run (and debug) TS?
By default it comes with Intellisense, Syntax Highlighting and debugging. It does not include the compiler.
// tsconfig.json
// compiled to ES5 and set CommonJS modules
// output out directory for js
// sourceMap for debugging
// be careful with commenting things out - there are no comments in json
// and build process just fails
{
"compilerOptions": {
"target": "ES5",
"module": "CommonJS",
"outDir": "out",
"sourceMap": true
}
}
I can now to Ctrl F5 which runs tsc and generates the js out file and runs the program
Debug Console in VS Code - this is the output! VS Code always defaulting to the terminal output.
Annoying that ctrl F5 doesn’t show the output always!
Ctrl , or File Preferences Settings
then
Debug: Internal Console Always Reveal change from openOnFirstSessionStart to openOnSessionStart… phew
AOC Day 1
// fs is a built-in module in Node.js for file system operations
// "@types/node": "^22.10.1" for dev dependencies
import * as fs from 'fs';
// Read the file synchronously
const fileContent = fs.readFileSync('1.txt', 'utf-8');
// Split the content into lines and map into an array of arrays
const data: number[][] = fileContent
.trim() // Remove extra newlines or spaces
.split('\n') // Split by lines
.map(line => line.split(/\s+/).map(Number)); // Split each line by spaces and convert to numbers
// Iterate over the data
for (const [a, b] of data) {
console.log(`a: ${a}, b: ${b}`);
}
and 1.txt
3 4
4 3
2 5
1 3
3 9
3 3
I noticed that in
// tsconfig.json
// **comments are bad here!!!**
{
"compilerOptions": {
// "target": "ES5",
"target": "ESNext",
"module": "CommonJS",
"outDir": "out",
"sourceMap": true,
"moduleResolution": "Node",
"types": [
"node"
]
}
}
This ran (albeit with warnings in VSCode about not being able to find module fs). But if I targeted ES5 then tsc didn’t know about the node module. So I have to import it using package.json.
{
"devDependencies": {
"@types/node": "^22.10.1"
}
}
Compile Time
Annoying compile time lag
npx tsc --extendedDiagnostics
Files: 149
...
Total time: 5.06s
and now doing on WSL side
Files: 149
Program time: 0.99s
...
Bind time: 0.33s
Total time: 1.32s
Better but still a bit laggy.. 0.92s is normal with no code changes. On more powerful desktop machine it is 0.38s / 0.29s with changes / no changes.
Day 1 Part 1
// AoC Day 1 - Part 1
// fs is a built-in module in Node.js for file system operations
// "@types/node": "^22.10.1" for dev dependencies
import * as fs from 'fs';
// Read the file synchronously into immutable string
// need utf-8 to avoid returning a buffer (for binary files)
const fileContent: string = fs.readFileSync('1full.txt', 'utf-8');
// Parse the file content into a 2D array of numbers
// no error checking or validation here
// brevity over robustness
const data: number[][] = fileContent
.split('\n') // Split the content into lines
.map(line => // Process each line
line.split(/\s+/) // Split the line by one or more whitespace characters
.map(Number) // Convert each part into a number
);
// Test data to help build program
// const datab: number[][] = [
// [3, 4],
// [4, 3],
// [2, 5],
// [1, 3],
// [3, 9],
// [3, 3]
// ];
// Extract the first column (left list) and second column (right list)
const leftList: number[] = data.map(row => row[0]); // [3, 4, 2, 1, 3, 3]
const rightList = data.map(row => row[1]); // [4, 3, 5, 3, 9, 3]
// this mutates the original array!
// The array's contents can be modified, but the reference itself cannot point to a new array.
// const leftListSorted = leftList.sort((a, b) => a - b); // [1, 2, 3, 3, 3, 4]
// ... spread operator makes a shallow copy of leftList
// so as not to mutate the original array
const leftListSorted = [...leftList].sort((a, b) => a - b); // [1, 2, 3, 3, 3, 4]
const rightListSorted =[...rightList].sort((a, b) => a - b); // [3, 3, 3, 4, 5, 9]
// Calculate the differences and sum them up
let totalDifference = 0;
for (let i = 0; i < leftListSorted.length; i++) {
const difference = Math.abs(leftListSorted[i] - rightListSorted[i]);
totalDifference += difference;
console.log(`Difference between element ${i + 1}: ${difference}`);
}
// The answer
console.log(`Total difference: ${totalDifference}`);
Const
Const ensures the variable binding cannot be reassigned to a different value. eg cannot assign data to another array
Const Arrays can be sorted, pop’d, pushed in place.
Strings are immutable with const ie any change could create a new string, thus with const can’t be changed
Immutability
Could use external libraries like immutable.js to help
Part 2
// How many times does the number 1 appear in the right list
// eg first number 3 appears 3 times in right list
// so similarity score is 3 * 3 = 9
// 4 is 4 * 1 = 4
// 2 is 2 * 0 = 0
let totalSimilarityScore = 0;
for (let i = 0; i < leftList.length; i++) {
const numberToFind = leftList[i];
// Count how many times the current number appears in the right list
const countInRightList = rightList.filter(x => x === numberToFind).length;
// Calculate the similarity score for the current number
const similarityScore = numberToFind * countInRightList;
// Add the similarity score to the total
totalSimilarityScore += similarityScore;
}
// smilarity score is 31 for test data
// real answer 21328497
console.log(`Total similarity score: ${totalSimilarityScore}`);
classic way of iterating
// ES6 way to iterate over arrays, strings, maps, etc.
for (const numberToFind of leftList) {
// Count occurrences of the current number in the right list
const countInRightList = rightList
.filter(value => value === numberToFind)
.length;
// Calculate and add the similarity score for this number
totalSimilarityScore += numberToFind * countInRightList;
}
I like this easy to understand and well commented code.
Day 2
Prettier code formatter - after doing Shift Alt F to format, I couldn’t go back to VS code formatter Ctrl , settings then. So I uninstalled prettier
- make it work
- make it right
- makt it fast
Here is my code which I refactored through ChatGPT.
- Focus on the art of beautiful code
- Favoured understandability over brevity eg no &&, no functions
- Explicitly declared variables as can be undefined as this is their startig state
// kebab-case.ts for filenames
import * as fs from "fs";
const fileContent: string = fs.readFileSync('2.txt', 'utf-8');
const data: number[][] = fileContent
.split('\n') // Split the content into lines
.map(line => // Process each line
line.split(/\s+/) // Split the line by one or more whitespace characters
.map(Number) // Convert each part into a number
);
// const data: number[][] = [
// [7, 6, 4, 2, 1],
// [1, 2, 7, 8, 9],
// [9, 7, 6, 2, 1],
// [1, 3, 2, 4, 5],
// [8, 6, 4, 4, 1],
// [1, 3, 6, 7, 9],
// ];
// PascalCase for class names and types
type Direction = "flat" | "up" | "down";
// camelCase for variables and functions
let totalSafe = 0;
// Take each row into an array
for (const row of data) {
let rowSafe = true; // Track if the current row is safe
let lastElement: number | undefined; // Previous element in the row
let lastDirection: Direction | undefined; // Previous direction
// Iterate over each element in the row
for (let i = 0; i < row.length; i++) {
const element = row[i];
if (i === 0) {
// Initialize the first element and continue to the next
lastElement = element;
continue;
}
// 1. Current element is smaller than the last
if (element < lastElement) {
if (i > 1) {
if (lastDirection != "down") {
rowSafe = false;
// break out of the loop as the row is not safe becuase the direction is not down
break;
}
}
const difference = lastElement - element;
if (difference > 3) {
rowSafe = false; // Unsafe due to a difference greater than 3
break;
}
lastElement = element;
lastDirection = "down";
}
// 2. Element is larger than the last element
else if (element > lastElement) {
if (i > 1) {
if (lastDirection != "up") {
rowSafe = false; // Unsafe due to a inconsistent direction with last element
break;
}
}
const difference = element - lastElement;
if (difference > 3) {
rowSafe = false; // Unsafe due to a difference greater than 3
break
}
lastElement = element;
lastDirection = "up";
}
// Element is the same as the last element
else {
rowSafe = false; // Unsafe due to consecutive identical elements
break;
}
}
if (rowSafe) {
totalSafe += 1;
}
}
console.log(`Total safe rows: ${totalSafe}`);
Day 2 Part 2
Using ChatGPT to help with syntax - actually GH Copilot guessed I needed the splice remove function. What a superpower!
Interestingly GPT 4o and 01-preview thought there was a bug as I wasn’t catching a case where [7,7,1,2,3] but I am.
import * as fs from "fs";
const fileContent: string = fs.readFileSync('2.txt', 'utf-8');
const data: number[][] = fileContent
.split('\n') // Split the content into lines
.map(line => // Process each line
line.split(/\s+/) // Split the line by one or more whitespace characters
.map(Number) // Convert each part into a number
);
// const data: number[][] = [
// [7, 6, 4, 2, 1],
// [1, 2, 7, 8, 9],
// [9, 7, 6, 2, 1],
// [1, 3, 2, 4, 5],
// [8, 6, 4, 4, 1],
// [1, 3, 6, 7, 9],
// ];
type Direction = "flat" | "up" | "down";
let totalSafe = 0;
// Take each row into an array
for (const row of data) {
// Part 2 - Problem Dampener.
// make new array with take out 0 then first etc.. elements... to see if it is safe
// if safe then exit
// A section
for (let j = -1; j < row.length; j++) {
const rowCopy = [...row]; // Make copy of array
if (j === -1) {
// Do nothing skip the first element as want to leave array as is to see if safe
} else {
rowCopy.splice(j, 1); // Remove element at index j to see if problem dampener works
}
let rowSafe = true; // Track if the current row is safe
let lastElement: number | undefined; // Previous element in the row
let lastDirection: Direction | undefined; // Previous direction
// B section
// Iterate over each element in rowCopy
for (let i = 0; i < rowCopy.length; i++) {
const element = rowCopy[i];
if (i === 0) {
// Initialize the first element and continue to the next
lastElement = element;
continue;
}
// 1. Current element is smaller than the last
if (element < lastElement) {
if (i > 1) {
if (lastDirection != "down") {
rowSafe = false;
// break out of the B loop as the row is not safe because the direction is not down
break;
}
}
const difference = lastElement - element;
if (difference > 3) {
rowSafe = false; // Unsafe due to a difference greater than 3
break;
}
lastElement = element;
lastDirection = "down";
}
// 2. Current element is larger than the last element
else if (element > lastElement) {
if (i > 1) {
if (lastDirection != "up") {
rowSafe = false; // Unsafe due to a inconsistent direction with last element
break;
}
}
const difference = element - lastElement;
if (difference > 3) {
rowSafe = false; // Unsafe due to a difference greater than 3
break
}
lastElement = element;
lastDirection = "up";
}
// Current element is the same as the last element
else {
rowSafe = false; // Unsafe due to consecutive identical elements
break;
}
}
if (rowSafe) {
totalSafe += 1;
break; // Exit out of A loop as row is safe
}
} // end of B section
} // end of A section
// 561
console.log(`Total safe rows: ${totalSafe}`);
Am favouring more declaritive programming style as it makes it easier to reason about (IMO), and debug.
But this is getting verbose, so time to abstract out logic into functions.
Interestingly I’ve found it quite simple to step through this screenful of code and write logic. Not too congnitibely abstract.
todo - lets find others solution in TS
Day 3 - regex
ChatGPT is pretty good at getting regex’s
Day 3 - part 2 - pop and push
Splitting apart a problem into very small steps was worth it here. It really helped me figure out and understand the problem.
Day 4
Rename symbol shortcut - F2
Quick fix copilot - ctrl .
Got an issue where the debugger was going to the .js file whilst stepping through code:
let counter = 0;
// 1. make a string - horizontal
for (let rowNumber = 0; rowNumber < data.length; rowNumber++) {
// why does debugger go into the js file here?
const stringToCheck: string = data[rowNumber].join('');
let xmasIndex = stringToCheck.indexOf('XMAS');
console.log(xmasIndex);
while (xmasIndex > -1) {
counter++;
// Continue searching from the next position after the current match
xmasIndex = stringToCheck.indexOf('XMAS', xmasIndex + 1);
}
}
the out/4.js.map file looks like it is generated fine.
had conflicting foo variable in differet scopes
Making a function
Word search solving strategy has been fun
- horizontal is fine (and reverse)
- vertical is fine (and reverse)
- diagonal - fun!