AoC 2024 day 4

const fs = require("fs")

const input = fs.readFileSync(__dirname + (process.argv.includes("--test") ? "/test.txt" : "/input.txt"), "utf8")

const parseInput = (rawInput) => rawInput.split(/\r?\n/).map((row) => row.split(""))

const data = parseInput(input)

const rows = data.length
const cols = data[0].length

// Directions for part 1
const directions = [
    [0, 1],
    [1, 0],
    [1, 1],
    [1, -1],
    [0, -1],
    [-1, 0],
    [-1, -1],
    [-1, 1]
]

// Check for XMAS in part 1
const checkWord = (x, y, dx, dy, grid, word) => {
    for (let i = 0; i < word.length; i++) {
        const nx = x + i * dx
        const ny = y + i * dy
        if (nx < 0 || ny < 0 || nx >= rows || ny >= cols || grid[ny][nx] !== word[i]) {
            return false
        }
    }
    return true
}

// Part 1: Count all occurrences of "XMAS"
const part1 = (grid) => {
    let count = 0
    const word = "XMAS"

    for (let x = 0; x < rows; x++) {
        for (let y = 0; y < cols; y++) {
            for (const [dx, dy] of directions) {
                if (checkWord(x, y, dx, dy, grid, word)) count++
            }
        }
    }
    return count
}

// Part 2: Count all "X-MAS" patterns
const part2 = (grid) => {
    let count = 0
    for (let x = 1; x < rows - 1; x++) {
        for (let y = 1; y < cols - 1; y++) {
            if (grid[x][y] === "A") {
                const tlbr =
                    (grid[x - 1][y - 1] === "M" && grid[x + 1][y + 1] === "S") ||
                    (grid[x - 1][y - 1] === "S" && grid[x + 1][y + 1] === "M")
                const trbl =
                    (grid[x - 1][y + 1] === "M" && grid[x + 1][y - 1] === "S") ||
                    (grid[x - 1][y + 1] === "S" && grid[x + 1][y - 1] === "M")
                if (tlbr && trbl) count++
            }
        }
    }
    return count
}

console.time("Part 1 Time")
console.log("Part 1:", part1(data))
console.timeEnd("Part 1 Time")

console.time("Part 2 Time")
console.log("Part 2:", part2(data))
console.timeEnd("Part 2 Time")