Advent of code

day-1.js

function calcFloor(input) {
  var up = 0,
      down = 0,
      basement = 0,
      i;
  
  for(i=0; i<input.length; i++) {
    input[i] === '(' ? up++ : down++;
    
    if(!basement) {
      if(down > up) {
        basement = i + 1;
      }
    }
  }
  
  return {
    floor: up - down,
    basement: basement
  };
}

day-12.js

// Regex approach, works for the first part only
function getBalance(string) {
  var regex = /-?\d+/g,
      result,
      balance = 0;
  
  while ((result = regex.exec(string)) !== null) {
    balance += parseInt(result[0], 10);
  }
  
  return balance;
}

day-2.js

function calcArea(input) {
  var result = {
    paper: 0,
    ribbon: 0
  };
  
  input.forEach(function (dimensions) {
    var sides = dimensions.split('x').map(Number).sort(),
        areas = [
          sides[0] * sides[1],
          sides[0] * sides[2],
          sides[1] * sides[2]
        ],
        perimeters = [
          2 * (sides[0] + sides[1]),
          2 * (sides[0] + sides[2]),
          2 * (sides[1] + sides[2])
        ];
    
    result.paper += Math.min.apply(null, areas) + (2 * areas[0]) + (2 * areas[1]) + (2 * areas[2]);
    result.ribbon += Math.min.apply(null, perimeters) + (sides[0] * sides[1] * sides[2]);
  });
  
  return result;
}

day-3.js

function getUniqueHouses(directions) {
  var grid = {
        '0,0': 1
      },
      moves = {
        '^': [0, 1],
        '>': [1, 0],
        'v': [0, -1],
        '<': [-1, 0]
      },
      current = [0, 0],
      curHash,
      move,
      i;
  
  for(i = 0; i < directions.length; i++) {
    move = moves[directions[i]];
    
    current[0] += move[0];
    current[1] += move[1];
    curHash = current.join(',');
    
    if(!grid[curHash]) {
      grid[curHash] = 0;
    }
    
    grid[curHash]++;
  }
  
  console.log(grid);
  
  return Object.keys(grid).length;
}

function getTwoUniqueHouses(directions) {
  var moves = {
        '^': [0, 1],
        '>': [1, 0],
        'v': [0, -1],
        '<': [-1, 0]
      },
      grid = {
        '0,0': 1
      },
      positions = {
        santa: [0, 0],
        robot: [0, 0]
      },
      curHash,
      move,
      current = 'santa',
      i;
  
  for(i = 0; i < directions.length; i++) {
    move = moves[directions[i]];
    
    positions[current][0] += move[0];
    positions[current][1] += move[1];
    curHash = positions[current].join(',');
    
    if(!grid[curHash]) {
      grid[curHash] = 0;
    }
    
    grid[curHash]++;
    
    current = (current === 'santa' ? 'robot' : 'santa');
  }
  
  console.log(grid);
  
  return Object.keys(grid).length;
}

day-4.js

// Node.js
var md5 = require('md5'),
    secret = 'iwrupvqb',
    prefix = '000000', // 000000 for the second one
    answer = 0,
    hash;

for(;;) {
  hash = md5(secret + answer);
  
  if(hash.indexOf(prefix) === 0) {
    console.log(answer);
    break;
  }
  
  answer++;
}

day-5.js

function isNiceString(string) {
  var vowels = ['a', 'e', 'i', 'o', 'u'],
      badStrings = ['ab', 'cd', 'pq', 'xy'],
      vowelCount = 0,
      substring,
      hasTwoInARow = false,
      i;
      
  for(i = 0; i < string.length; i++) {
    if(i !== string.length - 1) {
      if(string[i] === string[i + 1]) {
        hasTwoInARow = true;
      }
      
      if(badStrings.indexOf(string[i] + string[i + 1]) !== -1) {
        return false;
      }
    }
    
    if(vowels.indexOf(string[i]) != -1) {
      vowelCount++;
    }
  }
  
  return hasTwoInARow && vowelCount >= 3;
}

function countNiceString(input) {
  var count = 0;
  
  input.forEach(function (string) {
    if(isNiceString(string)) {
      count++;
    }
  });
  
  return count;
}

day-8.js

// Incomplete, ended up doing this "manually" with find and replace in Atom :/
function getEscapedLength(string) {
  return string.replace(/\\\\/g, '\\').replace(/\\"/g, '"').replace(/\\x[0-9a-f]{1,2}/g, '&').length - 2;
}

function getLengthDifference(input) {
  var unescaped = 0,
      escaped = 0;
  
  input.forEach(function (string) {
    unescaped += string.length;
    escaped += getEscapedLength(string);
  });
  
  return unescaped - escaped;
}

day-9.js

function lookAndSay(sequence, steps) {
  var newSequence,
      i,
      j;
      
  for(i = 0; i < steps; i++) {
    newSequence = [];
    
    for(j = 0; j < sequence.length; j++) {
      if(newSequence.length === 0 || sequence[j] !== newSequence[newSequence.length - 1][0]) {
        newSequence.push([sequence[j], 0]);
      }
      
      newSequence[newSequence.length - 1][1]++;
    }
    
    sequence = newSequence.reduce(function (prev, curr) { return prev + curr[1].toString() + curr[0].toString() }, '');
  }
  
  return sequence;
}