adv17.js

#!/usr/bin/env node

const fs = require('fs');

let contents = fs.readFileSync("adv17.txt", 'utf8').trim();

let coordinates = contents.split("\n").map(l => l.split(", ").map(e => e.split("=")).sort(a => a[0] == "y" ? -1 : 1).map(e => e[1].split("..").map(n => parseInt(n))));
let spring = [0, 500];

let perimeter = [
    [coordinates[0][0][0], coordinates[0][1][0]],
    [coordinates[0][0][0], coordinates[0][1][0]],
];

coordinates.forEach(c => {
    for (j = 0; j < 2; j++) {
        if (perimeter[0][j] > c[j][0])
            perimeter[0][j] = c[j][0]
        if (perimeter[1][j] < c[j][c[j].length-1])
            perimeter[1][j] = c[j][c[j].length-1]
    }
});

perimeter[0][1] -= 1;
perimeter[1][1] += 1;
let rightPerimeter = perimeter.map(p => p.slice());

perimeter[0][0] = spring[0];

function initScreen(perimeter, clays, spring) {
    let screen = new Array();
    for (let y = perimeter[0][0]; y <= perimeter[1][0]; y++) {
        screen[y] = new Array();
        for (let x = perimeter[0][1]; x <= perimeter[1][1]; x++)  {
            screen[y][x] = '.';
        }
    }

    clays.forEach(clay => {
        let minY = clay[0][0];
        let maxY = clay[0][clay[0].length-1];

        let minX = clay[1][0];
        let maxX = clay[1][clay[1].length-1];
        for (let y = minY; y <= maxY; y++)
            for (let x = minX; x <= maxX; x++)
                screen[y][x] = '#';
    });

    screen[spring[0]][spring[1]] = '+';
    return screen;
}

const DIRECTION_VERTICAL = [1, 0];
const DIRECTION_LEFT = [0, -1];
const DIRECTION_RIGHT = [0, 1];

function isPassable(symbol) {
    return symbol == '.' || symbol == '|';
}

function flow(screen, point, direction, symbol) {
    if (symbol === undefined)
        symbol = '|';

    let position = point.slice();
    position[0] += direction[0];
    position[1] += direction[1];

    while ( screen[position[0]] != null 
        && isPassable(screen[position[0]][position[1]])
    ) {

        screen[position[0]][position[1]] = symbol;

        if (direction != DIRECTION_VERTICAL) {
            let sd = screen[position[0] + DIRECTION_VERTICAL[0]]
                [position[1] + DIRECTION_VERTICAL[1]];
            if (sd == '|')
                return false;
            else if (sd == '.')
                return flow(screen, position, DIRECTION_VERTICAL);
        }

        position[0] += direction[0];
        position[1] += direction[1];

    }

    if (screen[position[0]] == null 
        || screen[position[0]][position[1]] == null)
        return false;

    if (direction == DIRECTION_VERTICAL) {

        let filledFloor;
        do {
            position[0] -= direction[0];
            position[1] -= direction[1];
            filledFloor = flow(screen, position, DIRECTION_LEFT);
            filledFloor = flow(screen, position, DIRECTION_RIGHT) && filledFloor;
            if (filledFloor) {
                flow(screen, position, DIRECTION_LEFT, '~');
                flow(screen, position, DIRECTION_RIGHT, '~');
                screen[position[0]][position[1]] = '~';
            }
        } while (filledFloor && position[0] != point[0])

        return position[0] == point[0];
    }

    return true;
}

function countWatertiles(screen, perimeter, waterSymbols) {
    let tiles = 0;
    for (let y = perimeter[0][0]; y <= perimeter[1][0]; y++)
        for (let x = perimeter[0][1]; x <= perimeter[1][1]; x++)
            if (waterSymbols.has(screen[y][x]))
                tiles ++
    return tiles;
}

function printScreen(screen, perimeter) {
    for (let y = perimeter[0][0]; y <= perimeter[1][0]; y++) {
        console.log(screen[y].slice(perimeter[0][1], perimeter[1][1]+1).join(""));
    }
}


let screen = initScreen(perimeter, coordinates, spring);
flow(screen, spring, DIRECTION_VERTICAL);

printScreen(screen, [perimeter[0], [perimeter[1][0], perimeter[0][1] + 80]]);

//console.log(coordinates);
// console.log(rightPerimeter);

console.log("Part One:",
    countWatertiles(screen, rightPerimeter, new Set(['~', '|'])));
console.log("Part Two:",
    countWatertiles(screen, rightPerimeter, new Set(['~'])));