Adv2018/d12/main.js

function read(cb) {
    require("fs").readFile('./input', 'utf8', (err, data) => {
        var world = new World();
        data.split("\n").forEach((l) => {
            if (l.startsWith("initial state: ")) {
                world.initializeState(l.substr(15));
            } else {
                var r = /([.#]+) => ([.#])/.exec(l);
                if (r)
                    world.rules[r[1]] = r[2];
            }
        });
        cb(world);
    });
}

function World() {
    this.initialState = [];
    this.rules = [];
    this.state = [];
    this.loop = 0;
    this.offset = 0;
}

World.prototype.initializeState = function(li) {
    for (var i =0, len = li.length; i < len; ++i)
        this.initialState.push(li[i] == '#');
    this.state = this.initialState;
}

World.prototype.arrToString = function(pos) {
    var result = "";
    for (var i =-2; i <= 2; ++i)
        result += (this.initialState[pos +i] ? '#' : '.');
    return result;
}

World.prototype.step = function() {
    this.state = [];
    var offset = [];
    for (var i =-2; i < 0; ++i) {
        var state = this.rules[this.arrToString(i)];
        if (state == '#')
            offset[-i] = true;
        else if (state == '.')
            offset[-i] = false;
    }
    for (var i =0, len = this.initialState.length +2; i < len; ++i) {
        var state = this.rules[this.arrToString(i)];
        if (state == '#')
            this.state[i] = true;
        else if (state == '.')
            this.state[i] = false;
    }
    if (offset[2]) {
        this.state.splice(0, 0, offset[2], offset[1])
        this.offset += 2;
    }
    else if (offset[1]) {
        this.state.splice(0, 0, offset[1])
        ++this.offset;
    }
    this.initialState = this.state;
    ++this.loop;
}

World.prototype.count = function() {
    var result = 0;
    for (var i =0, len = this.initialState.length; i < len; ++i)
        if (this.initialState[i])
            result += i -this.offset;
    return result;
}

World.prototype.run = function(max) {
    for (var i =0; i < max; ++i)
        this.step();
}

function ex1() {
    read(world => {
        world.run(20);
        console.log(world.count());
    });
}

function ex2() {
    read(world => {
        world.run(500);
        console.log(world.count() +(50000000000 -500) *36);
    });
}

ex1();
ex2();