AoC/2024/18/index.ts

const fs = require('fs');

const input = fs.readFileSync(__dirname + '/input.txt', 'utf8').split("\n");

interface Coord {
    x: number,
    y: number,
};

enum Dir {
    Up,
    Right,
    Down,
    Left,
};

const map: Array<Array<string>> = [];

const path: Array<Coord> = [];

const width = 71;
const height = 71;

for (let y = 0; y < height; y++) {
    if (!map[y]) {
        map[y] = [];
    }
    for (let x = 0; x < width; x++) {
        map[y][x] = '.';
    }
}

for (let i = 0; i < 1024; i++) {
    const [x, y] = input[i].split(',').map((st: string) => parseInt(st));
    map[y][x] = '#'
}

function get(pos: Coord): string {
    if (map[pos.y] && map[pos.y][pos.x]) {
        return map[pos.y][pos.x];
    }
    return '#';
}

function set(pos: Coord, val: string): void {
    map[pos.y][pos.x] = val;
}

function nextDir(dir: Dir): Dir {
    const directions = [Dir.Up, Dir.Right, Dir.Down, Dir.Left];
    const i = (directions.indexOf(dir) + 1) % directions.length;
    return directions[i];
}
function prevDir(dir: Dir): Dir {
    const directions = [Dir.Up, Dir.Right, Dir.Down, Dir.Left];
    const i = directions.indexOf(dir) - 1;
    if (i < 0) {
        return directions[directions.length - 1];
    }
    return directions[i];
}

function isBranch(pos: Coord, dir: Dir): boolean {
    const leftDir = prevDir(dir);
    const rightDir = nextDir(dir);
    const next = nextCoord(pos, dir);
    const left = nextCoord(pos, leftDir);
    const right = nextCoord(pos, rightDir);
    const nextChar = get(next);
    const leftChar = get(left);
    const rightChar = get(right);
    return nextChar === '.' && leftChar === '.'
        || nextChar === '.' && rightChar === '.'
        || leftChar === '.' && rightChar === '.';
}

function printMap(path: Array<Coord> = []) {
    const mapClone = map.slice().map((row: Array<string>) => row.slice());
    path.forEach(({ x, y }) => {
        mapClone[y][x] = 'O';
    });
    console.log(mapClone.map((row: Array<string>) => row.join('')).join("\n"));
    console.log("\n");
}

function nextCoord(pos: Coord, direction: Dir): Coord {
    return direction === Dir.Up ? { x: pos.x, y: pos.y - 1 }
        : (direction === Dir.Right ? { x: pos.x + 1, y: pos.y }
            : (direction === Dir.Down ? { x: pos.x, y: pos.y + 1 } : { x: pos.x - 1, y: pos.y })
        );
}

function isDeadEnd(pos: Coord): boolean {
    if ((pos.x === 0 && pos.y === 0) || (pos.x === width - 1 && pos.y === width - 1)) {
        return false;
    }
    const adjs = [Dir.Up, Dir.Right, Dir.Down, Dir.Left].map((dir) => get(nextCoord(pos, dir))).join('');
    return adjs === '###.'
        || adjs === '##.#'
        || adjs === '#.##'
        || adjs === '.###';
}

function fillDeadEnd(pos: Coord): void {
    set(pos, '#')
    for (let dir of [Dir.Up, Dir.Right, Dir.Down, Dir.Left]) {
        const next = nextCoord(pos, dir);
        if (get(next) === '.') {
            if (isDeadEnd(next)) {
                fillDeadEnd(next);
            }
        }
    };
}
printMap();

// for (let y = 0; y < height; y++) {
//     for (let x = 0; x < width; x++) {
//         const pos = { x, y };
//         const char = get(pos);
//         if (char !== '.') {
//             continue;
//         }
//         if (isDeadEnd(pos)) {
//             fillDeadEnd(pos);
//         }
//     }
// }

// printMap();

interface Nd {
    parent: Nd|null,
    pos: Coord,
    g: number,
    h: number,
    f: number,
};

const openList: Array<Nd> = [];
const closedList: Array<Nd> = [];

const startNode: Nd = {
    parent: null,
    pos: { x: 0, y: 0 },
    g: 0,
    h: 0,
    f: 0,
};

const endNode = {
    parent: null,
    pos: { x: width - 1, y: height - 1 },
    g: 0,
    h: 0,
    f: 0,
};

openList.push(startNode);

while (openList.length > 0) {
    let currentNode = openList[0];
    let currentIndex = 0;
    openList.forEach((item, index) => {
        if (item.f < currentNode.f) {
            currentNode = item;
            currentIndex = index;
        }
    });

    openList.splice(currentIndex, 1);
    closedList.push(currentNode);

    if (currentNode.pos.x === endNode.pos.x && currentNode.pos.y === endNode.pos.y) {
        let current: Nd|null = currentNode;
        while (current) {
            path.push(current.pos);
            current = current.parent;
        }

        break;
    }

    const children: Array<Nd> = [];

    [Dir.Up, Dir.Right, Dir.Down, Dir.Left].forEach((dir) => {
        const nodePos = nextCoord(currentNode.pos, dir);

        if (get(nodePos) === '#') {
            return;
        }

        const newNode: Nd = {
            parent: currentNode,
            pos: nodePos,
            g: 0,
            h: 0,
            f: 0,
        };

        if (closedList.find((closedChild) => closedChild.pos.x === newNode.pos.x && closedChild.pos.y === newNode.pos.y)) {
            return;
        }

        newNode.g = currentNode.g + 1;
        newNode.h = ((newNode.pos.x - endNode.pos.x) ** 2) + ((newNode.pos.y - endNode.pos.y) ** 2);
        newNode.f = newNode.g + newNode.h;

        if (openList.find((openNode) => newNode.pos.x === openNode.pos.x && newNode.pos.y === openNode.pos.y && newNode.g > openNode.g)) {
            return;
        }

        openList.push(newNode);
    });
}

printMap();
console.log(path, path.length)