advent-of-code-2023/day12/index.js

const fs = require("node:fs");

let data;
try {
  data = fs.readFileSync("test.txt", "utf8");
} catch (err) {
  return
}

const lines = data.trim().split("\n");
var part1 = 0;
var part2 = 0;

lines.forEach((l) => {
  const parts = l.split(" ");
  const map = parts[0];
  const damaged = parts[1].split(",").map(Number);
  // const all = allArrangements(map)
  // const valid = all.filter((m) => isValid(m, damaged));
  // part1 += valid.length;

  const map2 = [map, map, map, map, map].join("?");
  const damaged2 = [damaged, damaged, damaged, damaged, damaged].flat();
  // console.log(damaged2);
  const all2 = allValidArrangements(map2, damaged2);
  console.log("all2", all2);
  part2 += all2.length;
});

// console.log("part1", part1);
console.log("part2", part1);

function allValidArrangements(map, damaged, index = 0) {
  const i = map.substring(index).indexOf("?");
  if (i === -1) {
    return map;
  }

  const one = allValidArrangements(replaceAt(map, i + index, "#"), damaged, index + 1);
  const two = allValidArrangements(replaceAt(map, i + index, "."), damaged, index + 1);
  return [one, two].flat();
}


function allArrangements(map, index = 0) {
  const i = map.substring(index).indexOf("?");
  if (i === -1) {
    return map;
  }

  const one = allArrangements(replaceAt(map, i + index, "#"), index + 1);
  const two = allArrangements(replaceAt(map, i + index, "."), index + 1);
  return [one, two].flat();
}

function replaceAt(str, index, replacement) {
  return str.substring(0, index) + replacement + str.substring(index + replacement.length);
}

function isValid(map, damaged) {
  const trimmed = map.replace(/^\.+/, "").replace(/\.+$/, "");
  const parts = trimmed.split(/\.+/);
  let isValid = parts.length === damaged.length;
  damaged.forEach((d, i) => {
    if (!parts[i] || parts[i].length !== d) {
      isValid = false;
    }
  });

  return isValid;
}