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feat: day 15 warehouse woes 2/2 soln, #24 
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‎src/2024/2024-12-15/README.md‎

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Visit the Advent of Code website for more information on this puzzle at:
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**Source:** https://adventofcode.com/2024/day/15<br>
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**Status:** On-going ⭐
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**Status:** Complete ⭐⭐
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## Code
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- **`findInitialPosition()`** - Finds the robot's initial `Point` position in the 2D grid and stores them in the `this.pos` object
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- **`readInstruction()`** - Reads the next instruction and sets the (y,x) direction
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- **`walk()`** - Increments the robot's (y,x) coordinate by direction
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- **`next()`** - Finds the next (y,x) coordinate of the robot or a given `Point` parameter.
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- **`next()`** - Finds the **next** (y,x) coordinate of the robot or a given `Point` parameter using the robot's current direction.
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- **`prev()`** - Finds the robot's **previous** (y,x) coordinate or a given `Point` parameter using the robot's current direction.
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### `calculateGPS.ts`
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- **`moveBoxes()`** - Moves the robot and boxes across the grid
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- **`calculateGPS()`** - Calculates the GPS sum of all boxes in the grid
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### `calculateExpandedGPS.ts`
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- **`moveExpandedBoxes()`** - Moves the robot and the expanded (2x size) boxes across the grid.
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- **`calculateExpandedGPS()`** - Calculates the GPS sum of all expanded boxes in the grid.
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### `fileReader.ts`
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- **`fileReader()`** - Reads and formats the day 15 quiz input file.
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### `fileReaderExpanded.ts`
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- **`fileReader()`** - Reads and formats the day 15 - part 2 quiz input file. Expands the tile symbols by 2.
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## Notes
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### Main Objects

‎src/2024/2024-12-15/lib/calculateExpandedGPS.ts‎

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import type { Point, PointSymbol } from '@/aoc/point/types.js'
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import { getCoordinateSymbol, getGridDimensions, isOutOfBounds } from '@/aoc/grid/utils.js'
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import {
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getBoxStartCoordinates,
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getReverseSymbol,
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getSymbolDirection,
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isExpandedBoxSymbol
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} from './utils.js'
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import { Robot } from './robot.js'
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/**
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* Moves the robot and the expanded (2x size) boxes across the grid
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* @param {string[][]} grid - 2D string array containing walls, boxes and space data
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* @param {string[]} instructions - String array containing the robot's pushBox instructions
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* @returns {void}
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*/
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export const moveExpandedBoxes = (grid: string[][], instructions: string[]): void => {
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const dimensions = getGridDimensions(grid)
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const robot = new Robot(grid, instructions)
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while (robot.instructions.length > 0) {
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robot.readInstruction()
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let nextPos = robot.next()
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let nextSymbol = getCoordinateSymbol(nextPos, grid)?.symbol as string
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// Move robot to the next blank space
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if (nextSymbol === '.') {
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grid[robot.pos.y]![robot.pos.x] = '.'
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grid[nextPos.y]![nextPos.x] = robot.symbol
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robot.walk()
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}
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if (isExpandedBoxSymbol(nextSymbol)) {
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// Move boxes along the horizontal x-axis
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if (robot.direction.x !== 0) {
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const boxes: Point[] = [nextPos]
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while (!isOutOfBounds(nextPos, dimensions) && isExpandedBoxSymbol(nextSymbol)) {
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nextPos = robot.next(nextPos)
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nextSymbol = getCoordinateSymbol(nextPos, grid)?.symbol as string
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if (isExpandedBoxSymbol(nextSymbol)) {
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boxes.push(nextPos)
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}
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}
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// Move groups of boxes if there's a space at their end
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if (nextSymbol === '.' && boxes.length > 0) {
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for (let i = boxes.length - 1; i >= 0; i -= 1) {
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const next = robot.next(boxes[i])
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const temp = grid[boxes[i]!.y]![boxes[i]!.x] as string
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grid[boxes[i]!.y]![boxes[i]!.x] = '.'
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grid[next.y]![next.x] = temp
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}
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// Move the robot
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grid[robot.pos.y]![robot.pos.x] = '.'
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robot.walk()
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grid[robot.pos.y]![robot.pos.x] = robot.symbol
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}
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}
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// Move boxes along the vertical y-axis
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if (robot.direction.y !== 0) {
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// 1st box after the robot
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const { side1, side2 } = getBoxStartCoordinates(nextPos, grid)
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let start = { ...side1 }
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const visited: PointSymbol[] = []
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const retrace: PointSymbol[] = [side2]
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let canMove = true
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while (start && isExpandedBoxSymbol(start.symbol)) {
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const next = robot.next(start)
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const nextSym = getCoordinateSymbol(next, grid)!.symbol
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// Store the visited box coordinates
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visited.push(start)
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if (['.', '#'].includes(nextSym as string)) {
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// End of line reached (space or wall): Retrace unvisited connected coordinates
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start = retrace.pop() as PointSymbol
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// Connected boxes will not move at anytime a wall `#` is encountered
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if (nextSym === '#') {
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canMove = false
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}
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} else if (nextSym === start.symbol) {
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// Found stack of boxes:
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// Move to the next (up/down) coordinate if its symbol is similar to the current symbol
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start = { ...next } as PointSymbol
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start.symbol = getCoordinateSymbol(start, grid)!.symbol
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} else if (nextSym === getReverseSymbol(start.symbol)) {
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// Found half-stacked boxes:
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// Stack the next coordinate if it's symbol is different from the current symbol
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retrace.push({ ...next, symbol: nextSym })
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// Move to the next diagonally-aligned half-box symbol coordinate
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const xDirection = getSymbolDirection(nextSym)
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if (xDirection) {
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start = { ...next, x: next.x + xDirection } as PointSymbol
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start.symbol = getCoordinateSymbol(start, grid)!.symbol
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}
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}
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}
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// Move the boxes
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if (canMove) {
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visited
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.sort((a, b) => {
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if (robot.direction.y < 0) {
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return (a.y < b.y ? -1 : 1)
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} else {
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return (a.y > b.y ? -1 : 1)
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}
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})
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.forEach(item => {
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const next = robot.next(item)
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grid[item.y]![item.x] = '.'
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grid[next.y]![next.x] = item.symbol
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})
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grid[robot.pos.y]![robot.pos.x] = '.'
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grid[nextPos.y]![nextPos.x] = robot.symbol
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robot.walk()
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}
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}
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}
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}
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}
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/**
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* Calculates the GPS sum of all expanded boxes in the grid
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* @param {string[][]} grid - 2D string array containing walls, boxes and space data
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* @returns {number} GPS sum of all boxes in the grid
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*/
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export const calculateExpandedGPS = (grid: string[][]): number => {
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const dimensions = getGridDimensions(grid)
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let sumGPS = 0
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for (let y = 0; y < dimensions.length; y += 1) {
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for (let x = 0; x < dimensions.width; x += 1) {
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if (grid[y]![x] === '[') {
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sumGPS += y * 100 + x
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}
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}
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}
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return sumGPS
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}

‎src/2024/2024-12-15/lib/fileReaderExpanded.ts‎

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import type { RobotWarehouseData } from './types.js'
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import { AOCOutputType, readAOCInputFile } from '@/aoc/file/aocfile.js'
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import { file } from '@/aoc/file/utils.js'
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/**
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* Reads and formats the day 15 - part 2 quiz input file. Expands the tile symbols by 2.
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* @param {string} fileName - Input text filename path relative to this script
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* @returns {RobotWarehouseData} Quiz input data
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*/
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export const fileReaderExpand = (fileName: string): RobotWarehouseData => {
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const input = readAOCInputFile({
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filePath: file(import.meta.url, fileName),
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type: AOCOutputType.STRING
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}) as string
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return input
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.split('\n\n')
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.reduce((data, item, index) => {
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// Grid
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if (index === 0) {
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return {
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...data,
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grid: item
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.split('\n')
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.map(line => line.split(''))
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.reduce((list: string[][], tiles) => {
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const processed = tiles.reduce((subList: string[], elem) => {
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if (['.', '#'].includes(elem)) {
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subList.push(elem, elem)
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} else if (elem === 'O') {
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subList.push('[', ']')
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} else if (elem === '@') {
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subList.push('@', '.')
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}
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return subList
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}, [])
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return [...list, processed]
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}, [])
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}
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}
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// Instructions
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return {
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...data,
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instructions: item
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.split('')
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.reverse()
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.filter(direction => direction !== '\n')
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}
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}, {}) as RobotWarehouseData
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}

‎src/2024/2024-12-15/lib/robot.ts‎

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}
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/**
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* Finds the next (y,x) coordinate of the robot or a given `Point` parameter.
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* Finds the next (y,x) coordinate of the robot or a given `Point` parameter using the robot's current direction.
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* @param {Point} [point] - (Optional) (y,x) coordinate to find the next step coorndinate from
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* @returns {Point} Next (y,x) coordinate after 1 step
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*/
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x: nextX, y: nextY
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}
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}
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/**
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* Finds the robot's previous (y,x) coordinate or a given `Point` parameter using the robot's current direction.
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* @param {Point} [point] - (Optional) (y,x) coordinate to find the previous step coorndinate from
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* @returns {Point} Next (y,x) coordinate before the provided coordinate
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*/
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prev (point?: Point): Point {
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const x = point?.x || this.pos.x
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const y = point?.y || this.pos.y
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const nextX = x - this.direction.x
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const nextY = y - this.direction.y
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return {
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x: nextX, y: nextY
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}
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}
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}

‎src/2024/2024-12-15/lib/utils.ts‎

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import type { Point, PointSymbol } from '@/aoc/point/types.js'
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import { getCoordinateSymbol } from '@/aoc/grid/utils.js'
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/**
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* Checks if the `symbol` parameter is an expanded box symbol
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* @param {string} symbol - String character representing an expanded box symbol
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* @returns {boolean} Flag indicating if the `symbol` character is a box symbol
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*/
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export const isExpandedBoxSymbol = (symbol: string) => ['[', ']'].includes(symbol as string)
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/**
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* Retrieves the 2 half-box (y,x) coordinates of a full expanded box - left and right `PointSymbol`
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* @param {Point} point - (x,y) coordinate of one side of the box
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*/
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export const getBoxStartCoordinates = (point: Point, grid: string[][]):
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{ side1: PointSymbol, side2: PointSymbol } => {
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const rightCoord = { ...point, x: point.x + 1 }
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const leftCoord = { ...point, x: point.x - 1 }
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let side2: PointSymbol = { x: -1, y: -1, symbol: '-' }
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const symbol = getCoordinateSymbol(point, grid)?.symbol as string
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const right = getCoordinateSymbol(rightCoord, grid)?.symbol as string
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const left = getCoordinateSymbol(leftCoord, grid)?.symbol as string
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if (`${symbol}${right}` === '[]') {
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side2 = { ...side2, ...rightCoord, symbol: right }
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}
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if (`${left}${symbol}` === '[]') {
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side2 = { ...side2, ...leftCoord, symbol: left }
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}
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const side1 = { ...point, symbol }
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return {
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side1,
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side2
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}
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}
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/**
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* Retrieves the reverse matching symbol of an expanded box symbol
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* @param {string} symbol - String character representing an expanded box symbol
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* @returns {string | undefined} Reverse matching symbol of an expanded box symbol or `undefined`
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*/
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export const getReverseSymbol = (symbol: string): string | undefined => {
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if (!['[', ']'].includes(symbol)) return
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return symbol === '[' ? ']' : '['
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}
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/**
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* Retrieves the `x` direction associated with an expanded box symbol
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* @param symbol - String character representing an expanded box symbol
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* @returns {number | undefined}
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*/
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export const getSymbolDirection = (symbol: string): number | undefined => {
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if (!['[', ']'].includes(symbol)) return
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let xDirection = 0
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if (symbol === '[') xDirection = 1
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if (symbol === ']') xDirection = -1
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return xDirection
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}

‎src/2024/2024-12-15/main.ts‎

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import { fileReader } from './lib/fileReader.js'
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import { fileReaderExpand } from './lib/fileReaderExpanded.js'
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import { moveBoxes, calculateGPS } from './lib/calculateGPS.js'
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import { moveExpandedBoxes, calculateExpandedGPS } from './lib/calculateExpandedGPS.js'
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/**
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* Part 1/2 of the 2024-12-15 quiz
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moveBoxes(grid, instructions)
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const gps = calculateGPS(grid)
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console.log('---GPS', gps)
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console.log('Part 1: Regular boxes GPS:', gps)
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}
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/**
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* Part 2/2 of the 2024-12-15 quiz
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* Moves the robot, expanded boxes and calculates all expanded boxes' GPS
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*/
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const quiz20241215_02 = () => {
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const { grid, instructions } = fileReaderExpand('../input.txt')
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moveExpandedBoxes(grid, instructions)
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const gps = calculateExpandedGPS(grid)
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console.log('Part 2: Expanded boxes GPS:', gps)
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}
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quiz20241215_01()
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quiz20241215_02()

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