Advent of Code

day2.js

const { deepStrictEqual } = require('assert');
const fs = require('fs');

const ADDITION = 1;
const MULTIPLCATION = 2;
const EOF = 99;
const DEBUG = false;

function executeProgram(input) {
  const program = input.split(',').map((v) => parseInt(v));
  var pointer = 0;
  DEBUG && console.log('program', program);

  while(pointer < program.length) {
    const pointerValue = program[pointer];
    let outputPointer = program[pointer + 3];

    switch(pointerValue) {
      case ADDITION:
        program[outputPointer] = add(program, pointer);
        pointer += 4;
        break;
      case MULTIPLCATION:
        program[outputPointer] = multiply(program, pointer);
        pointer += 4;
        break;
      case EOF:
        return program.join(',');
      default:
        throw new Error('Unknown instruction. ' + pointerValue);
    }
  }

  return input;
}

function add(program, pointer) {
  DEBUG && console.log('add', program, pointer);
  let aPointer = program[pointer + 1];
  let bPointer = program[pointer + 2];

  DEBUG && console.log(program[aPointer], ' + ', program[bPointer]);

  return program[aPointer] + program[bPointer];
}

function multiply(program, pointer) {
  DEBUG && console.log('multiply', program, pointer);
  let aPointer = program[pointer + 1];
  let bPointer = program[pointer + 2];
  DEBUG && console.log(program[aPointer], ' * ', program[bPointer]);

  return program[aPointer] * program[bPointer];
}

console.log('executeProgram Tests');
deepStrictEqual(executeProgram('1,0,0,0,99'), '2,0,0,0,99');
deepStrictEqual(executeProgram('2,3,0,3,99'), '2,3,0,6,99');
deepStrictEqual(executeProgram('2,4,4,5,99,0'), '2,4,4,5,99,9801');
deepStrictEqual(executeProgram('1,1,1,4,99,5,6,0,99'), '30,1,1,4,2,5,6,0,99');
deepStrictEqual(executeProgram('1,9,10,3,2,3,11,0,99,30,40,50'), '3500,9,10,70,2,3,11,0,99,30,40,50');


// Part 2
const input = fs.readFileSync('./input.txt', 'utf8');

function findCorrectProgram() {

  for (var noun = 0; noun <= 99; noun++) {
    for(var verb = 0; verb <= 99; verb++) {
      var p = input.split(',');

      p[1] = noun;
      p[2] = verb;

      var output = executeProgram(p.join(',')).split(',');
      if (output[0] === '19690720') {
        console.log(100 * noun + verb);
        console.log('Matched Program', output.join(','));
      }
    }
  }
}

findCorrectProgram();