feat: day 8 resonant collinearity 20241208

README.md

@@ -1,6 +1,8 @@
 ## ✨ adventofcode
 
-This repository contains solutions and a local development environment for the [Advent of Code](https://adventofcode.com/) event puzzles.
+This repository contains solutions and a local development environment for the [Advent of Code](https://adventofcode.com/) event puzzles using TypeScript/JavaScript.
+
+The codes are structured in a way that discusses and walks through the solution steps for the AoC quizzes rather than focusing on AoC's competitive programming.
 
 ### 🎄 Advent of Code Quiz Information
 
@@ -14,6 +16,7 @@ This repository contains solutions and a local development environment for the [
 - Day 5: Print Queue [[link]](/src/2024/2024-12-05/README.md)
 - Day 6: Guard Gallivant [[link]](/src/2024/2024-12-06/README.md)
 - Day 7: Bridge Repair [[link]](/src/2024/2024-12-07/README.md)
+- Day 8: Resonant Collinearity [[link]](/src/2024/2024-12-08/README.md)
 
 </details>
 
@@ -110,7 +113,7 @@ Using Node
    npm run transpile
    node dist/sample/sample.js
    ```
-4. See the [Available Scripts](#available-scripts) section for more information.
+4. See the [Available Scripts](#-available-scripts) section for more information.
 
 ## ⚡ Alternate Usage
 

src/2024/2024-12-08/README.md

@@ -0,0 +1,22 @@
+## Day 8: Resonant Collinearity
+
+Visit the Advent of Code website for more information on this puzzle at:
+
+**Source:** https://adventofcode.com/2024/day/8<br>
+**Status:** Complete ⭐⭐
+
+## Code
+
+### `GridAntinodes.ts`
+
+- `GridAntiNodes` class - Object that tracks and manages `Antennas` and `Antinodes` in a 2D grid array
+
+### `uniqueAntinodes.ts`
+
+- `uniqueAntinodes()` - Counts the unique locations in the grid that contains an antinode
+
+### `allAntinodes.ts`
+
+- `getAntinodesInPath()` - Finds all `Antinode` coordinates along a path within a 2D array (grid) given a `Point`, increment steps and a +/- direction
+
+- `countAllAntinodes()` - Counts the unique locations in the grid that contains all locations of antinodes along a path

src/2024/2024-12-08/input.txt

@@ -0,0 +1,12 @@
+............
+........x...
+.....x......
+.......x....
+....x.......
+......B.....
+............
+............
+........B...
+.........B..
+............
+............

src/2024/2024-12-08/lib/GridAntinodes.ts

@@ -0,0 +1,105 @@
+import type { Antenna } from './types.js'
+
+/**
+ * @class GridAntiNodes
+ * @description Object that tracks `Antennas` and `Antinodes` in a 2D grid array
+ */
+export class GridAntiNodes {
+  /** 2D string user input array */
+  board: string[][] = []
+
+  /** Array containing Antenna (y,x) coordinates */
+  antennas: Antenna[] = []
+
+  /** List of unique Antinode (y,x) coordinate strings */
+  antinodes = new Set<string>()
+
+  /** Grid array index pointing to the current antenna in the `this.antennas[]` list */
+  currentAntIndex: number = 0
+
+  /** Grid array index pointing to the next antenna after `this.currentAntIndex` */
+  nextAntIndex: number = 1
+
+  /**
+   * Creates an instance of the `GridAntiNodes` class
+   * @constructor
+   * @param {string[][]} inputFile 2D string array containing grid paths and `Antennas`
+   */
+  constructor(inputFile: string[][]) {
+    this.board = inputFile
+    this.findAntennas()
+  }
+
+  /**
+   * Finds and stores the (x,y) coordinates of valid `Antennas`
+   * from the 2D string array into the `this.antennas[]` array
+   */
+  findAntennas (): void {
+    for (let row = 0; row < this.board.length; row += 1) {
+      const indices: Antenna[] = this.board[row]!.reduce((list: Antenna[], item, index) => {
+        if (item.match(/^[A-Za-z0-9]+$/g)) {
+          this.board[row]![index] = item
+
+          return [
+            ...list, { frequency: item, x: index, y: row }
+          ]
+        }
+
+        return list
+      }, [])
+
+      this.antennas = [...this.antennas, ...indices]
+    }
+  }
+
+  /**
+   * Increments the index counters used in traversing the `Antinodes` list
+   */
+  incrementCursors (): void {
+    if (this.nextAntIndex === this.antennas.length - 1) {
+      this.currentAntIndex += 1
+      this.nextAntIndex = this.currentAntIndex + 1
+    } else {
+      this.nextAntIndex += 1
+    }
+  }
+
+  /**
+   * Resets the index counters used in traversing the `Antinodes` list
+   */
+  resetCursors (): void {
+    this.currentAntIndex = 0
+    this.nextAntIndex = 1
+  }
+
+  /**
+   * Stores the (x,y) coordinates of an `Antinode`
+   * @param {string} antinodeCoord String-concatenated (x,y) coordinate of an `Antinode`
+   */
+  storeAntinode (antinodeCoord: string): void {
+    this.antinodes.add(antinodeCoord)
+  }
+
+  /**
+   * Prints the 2D grid (board) to the screen
+   * @param {boolean} withAntinodes Flag to display the `Antinodes` in the grid
+   */
+  printGrid (withAntinodes: boolean = false): void {
+    if (withAntinodes) {
+      const printBoard = structuredClone(this.board)
+
+      for (const antinode of this.antinodes) {
+        const coord = (antinode as string).split(',').map(item => Number(item))
+        const character = this.board[coord[0] as number]![coord[1] as number]
+
+        if (character === '.') {
+          printBoard[coord[0] as number]![coord[1] as number] = '#'
+        }
+      }
+
+      console.log(printBoard.map(row => row.join(' ')))
+    } else {
+      console.log(this.board.map(row => row.join(' ')))
+    }
+  }
+}

src/2024/2024-12-08/lib/allAntinodes.ts

@@ -0,0 +1,93 @@
+import type { Antenna, Point } from './types.js'
+import { GridAntiNodes } from './GridAntinodes.js'
+
+/**
+ * Finds all `Antinode` coordinates along a path within a 2D array (grid) given a `Point`, increment steps and a +/- direction
+ * @param {Point} point (y,x) coordinate of an `Antenna` qualified for creating an `Antinode`
+ * @param {Point} increments Amount of increments to increase/decrease the (y,x) offsets of a `Point`
+ * @param {number} direction `+/-` positive or negative direction for increasing/decreasing a `Point`'s coordinates
+ * @typedef {Object} board Dimensions of the 2D grid array
+ * @param {number} board.length Length of the 2D array
+ * @param {number} board.width Width of the 2D array
+ * @returns {Set<string>} All `Antinode` (y,x) coordinates along the path
+ */
+const getAntinodesInPath = (
+  point: Point,
+  increments: Point,
+  direction: number,
+  board: { length: number, width: number  }
+): Set<string> => {
+  const antinodes = new Set<string>()
+  const startPoint = { ...point }
+
+  while (
+    startPoint.x >= 0 && startPoint.x < board.length &&
+    startPoint.y >= 0 && startPoint.y < board.width
+  ) {
+    antinodes.add(`${startPoint.y},${startPoint.x}`)
+
+    startPoint.x += increments.x * direction
+    startPoint.y += increments.y * direction
+  }
+
+  return antinodes
+}
+
+/**
+ * Counts the unique locations in the grid that contains all locations of antinodes along a path
+ * @param {string[][]} inputFile 2D string array containing grid paths and `Antennas`
+ * @returns {number} Total number of unique antinodes in the grid
+ */
+export const countAllAntinodes = (inputFile: string[][]): number => {
+  const grid = new GridAntiNodes(inputFile)
+
+  while(grid.currentAntIndex < grid.antennas.length - 1) {
+    // Antennas
+    const a1 = grid.antennas[grid.currentAntIndex] as Antenna
+    const a2 = grid.antennas[grid.nextAntIndex] as Antenna
+
+    const gridDimensions = {
+      length: grid.board.length,
+      width: grid.board[0]!.length
+    }
+
+    // Skip processing antennas with different frequencies
+    if (a1.frequency !== a2.frequency) {
+      grid.incrementCursors()
+      continue
+    }
+
+    // Antenna coordinate difference
+    const diff = {
+      x: a2.x - a1.x,
+      y: a2.y - a1.y
+    }
+
+    if (
+      a1.y < inputFile.length && a1.y >= 0 &&
+      a1.x < inputFile[0]!.length && a1.x >= 0
+    ) {
+      // Find all aligned antinodes
+      getAntinodesInPath(a1, diff, -1, gridDimensions)
+        .forEach(
+          item => grid.antinodes.add(item)
+        )
+    }
+
+    if (
+      a2.y < inputFile.length && a2.y >= 0 &&
+      a2.x < inputFile[0]!.length && a2.x >= 0
+    ) {
+      // Find all aligned antinodes
+      getAntinodesInPath(a2, diff, 1, gridDimensions)
+        .forEach(
+          item => grid.antinodes.add(item)
+        )
+    }
+
+    grid.incrementCursors()
+  }
+
+  grid.printGrid(true)
+  return grid.antinodes.size
+}

src/2024/2024-12-08/lib/types.ts

@@ -0,0 +1,8 @@
+export interface Point {
+  x: number;
+  y: number;
+}
+
+export interface Antenna extends Point {
+  frequency: string;
+}

src/2024/2024-12-08/lib/uniqueAntinodes.ts

@@ -0,0 +1,60 @@
+import type { Antenna, Point } from './types.js'
+import { GridAntiNodes } from './GridAntinodes.js'
+
+/**
+ * Counts the unique locations in the grid that contains an antinode
+ * @param {string[][]} inputFile 2D string array containing grid paths and `Antennas`
+ * @returns {number} Total number of unique antinodes in the grid
+ */
+export const countAntinodes = (inputFile: string[][]): number => {
+  const grid = new GridAntiNodes(inputFile)
+
+  while(grid.currentAntIndex < grid.antennas.length - 1) {
+    // Antennas
+    const a1 = grid.antennas[grid.currentAntIndex] as Antenna
+    const a2 = grid.antennas[grid.nextAntIndex] as Antenna
+
+    // Skip processing antennas with different frequencies
+    if (a1.frequency !== a2.frequency) {
+      grid.incrementCursors()
+      continue
+    }
+
+    // Antenna coordinate difference
+    const diff = {
+      x: a2.x - a1.x,
+      y: a2.y - a1.y
+    }
+
+    // Antinode 1 coordinates
+    const node1: Point = {
+      x: a1.x - diff.x,
+      y: a1.y - diff.y
+    }
+
+    // Antinode 2 coordinates
+    const node2: Point = {
+      x: a2.x + diff.x,
+      y: a2.y + diff.y
+    }
+
+    if (
+      node1.y < inputFile.length && node1.y >= 0 &&
+      node1.x < inputFile[0]!.length && node1.x >= 0
+    ) {
+      grid.storeAntinode(`${node1.y},${node1.x}`)
+    }
+
+    if (
+      node2.y < inputFile.length && node2.y >= 0 &&
+      node2.x < inputFile[0]!.length && node2.x >= 0
+    ) {
+      grid.storeAntinode(`${node2.y},${node2.x}`)
+    }
+
+    grid.incrementCursors()
+  }
+
+  grid.printGrid(true)
+  return grid.antinodes.size
+}

src/2024/2024-12-08/main.ts

@@ -0,0 +1,32 @@
+import path from 'path'
+import { AOC_OUTPUT_TYPE, readAOCInputFile } from '@/utils/aocInputFile.js'
+import { currentDirectory } from '@/utils/file.js'
+
+import { countAntinodes } from './lib/uniqueAntinodes.js'
+import { countAllAntinodes } from './lib/allAntinodes.js'
+
+const input = readAOCInputFile({
+  filePath: path.join(currentDirectory(import.meta.url), 'input.txt'),
+  type: AOC_OUTPUT_TYPE.STRING_ARRAY_2D
+}) as string[][]
+
+/**
+ * Part 1/2 of the 2024-12-08 quiz
+ * Counts the unique locations in the grid that contains an antinode
+ */
+const quiz20241208_01 = () => {
+  const count = countAntinodes(input)
+  console.log('Antinodes in unique locations:', count)
+}
+
+/**
+ * Part 2/2 of the 2024-12-08 quiz
+ * Counts the unique locations in the grid of all antinodes that contains an antinode
+ */
+const quiz20241208_02 = () => {
+  const count = countAllAntinodes(input)
+  console.log('All Antinodes count:', count)
+}
+
+quiz20241208_01()
+quiz20241208_02()

src/2024/2024-12-08/sample.test.ts

@@ -0,0 +1,21 @@
+import path from 'path'
+import { test, expect } from 'vitest'
+
+import { AOC_OUTPUT_TYPE, readAOCInputFile } from '@/utils/aocInputFile.js'
+import { currentDirectory } from '@/utils/file.js'
+
+import { countAntinodes } from './lib/uniqueAntinodes.js'
+import { countAllAntinodes } from './lib/allAntinodes.js'
+
+const input = readAOCInputFile({
+  filePath: path.join(currentDirectory(import.meta.url), 'input.txt'),
+  type: AOC_OUTPUT_TYPE.STRING_ARRAY_2D
+}) as string[][]
+
+test('Antinodes in unique locations', () => {
+  expect(countAntinodes(input)).toBe(14)
+})
+
+test('All antinodes in line', () => {
+  expect(countAllAntinodes(input)).toBe(34)
+})