AoC2020_Day14.js

let input1 = ``;

let input = input2.split("\n");

function dec2bin(dec) {
  return (dec >>> 0).toString(2);
}

function part1() {
  const mem = {};
  let mask = "";
  for (let i = 0; i < input.length; i++) {
    const [left, right] = input[i].split(" = ");
    if (left === "mask") {
      mask = right;
    } else {
      const memLoc = left.replace(/(mem\[|\])/g, "");
      const binVal = dec2bin(Number(right));
      const value = new Array(36 - binVal.length)
        .fill("0")
        .concat(binVal.split(""));

      for (let m = 0; m < mask.length; m++) {
        const maskBit = mask[m];
        if (maskBit !== "X") {
          value[m] = maskBit;
        }
      }

      mem[memLoc] = parseInt(value.join(""), 2);
    }
  }

  console.log(Object.values(mem).reduce((a, b) => a + b, 0));
}

function getXIndices(value) {
  const res = [];
  for (let i = 0; i < value.length; i++) {
    if (value[i] === "X") {
      res.push(i);
    }
  }
  return res;
}

function part2() {
  const mem = {};
  let mask = "";
  for (let i = 0; i < input.length; i++) {
    const [left, right] = input[i].split(" = ");
    if (left === "mask") {
      mask = right;
    } else {
      const memLoc = left.replace(/(mem\[|\])/g, "");
      const binVal = dec2bin(Number(memLoc));
      const value = new Array(36 - binVal.length)
        .fill("0")
        .concat(binVal.split(""));

      let xCounter = 0;
      for (let m = 0; m < mask.length; m++) {
        const maskBit = mask[m];
        if (maskBit !== "0") {
          value[m] = maskBit;
        }
        if (maskBit === "X") {
          xCounter++;
        }
      }

      const xIndices = getXIndices(value);
      for (let f = 0; f < Math.pow(2, xCounter); f++) {
        const fMask = dec2bin(String(f)).padStart(xCounter, "0").split("");
        for (let h = 0; h < fMask.length; h++) {
          value[xIndices[h]] = fMask[h];
        }
        mem[parseInt(value.join(""), 2)] = Number(right);
      }
    }
  }

  console.log(Object.values(mem).reduce((a, b) => a + b, 0));
}

part2();