Adv2018/d02/main.js

const fs = require('fs');

function Box(str) {
    this.hash = str;

    var letters = {};
    for (var i=0; i < this.hash.length; ++i) {
        var l = this.hash[i];
        if (letters[l] === undefined)
            letters[l] = 0;
        letters[l]++;
    }
    this.lettersByCount = {};
    for (var i in letters)
        if (this.lettersByCount[letters[i]] === undefined)
            this.lettersByCount[letters[i]] = true;
}

Box.prototype.compareWith = function(other) {
    var diff = -1;
    for (var i=0, len=Math.min(this.hash.length, other.hash.length); i < len; ++i)
        if (this.hash[i] != other.hash[i]) {
            if (diff != -1)
                return false;
            diff = i;
        }
    return diff == -1 ? false : diff;
}

function read(cb) {
    fs.readFile('./input', 'utf8', (err, data) => {
        var lines = [];
        data.split("\n").forEach((line) => {
            if (line.length > 0)
                lines.push(new Box(line));
        });
        cb(lines);
    });
}

function ex1() {
    read(function(boxes) {
        var count3 = 0,
            count2 = 0;
        boxes.forEach(function(box) {
            if (box.lettersByCount[3])
                count3++;
            if (box.lettersByCount[2])
                count2++;
        });
        console.log(count2 * count3);
    });
}

function ex2() {
    read(function(boxes) {
        for (var i=0; i <boxes.length -1; ++i)
            for (var j =i+1; j < boxes.length; ++j) {
                var diff = boxes[i].compareWith(boxes[j]);
                if (diff !== false) {
                    console.log(boxes[i].hash.substr(0, diff) +boxes[i].hash.substr(diff +1));
                    return;
                }
            }
    });
}

ex1();
ex2();