function part1(inputText) {
  let beams = new Set([inputText.indexOf('S')]);
  const beamSplits = new Set();
  const lines = inputText.trimEnd().split('\n');
  for (let y = 1; y < lines.length; y++) {
    const nextBeams = new Set();
    for (const beamX of beams) {
      if (lines[y][beamX] === '.') {
    nextBeams.add(beamX);
      } else if (lines[y][beamX]) {
    beamSplits.add([beamX, y].toString());
    nextBeams.add(beamX + 1);
    nextBeams.add(beamX - 1);
      }
    }
    beams = nextBeams;
  }
  return beamSplits.size;
}

{
  const start = performance.now();
  const result = part1(document.body.textContent);
  const end = performance.now();
  console.info({ day: 7, part: 1, time: end - start, result });
}


function part2(inputText) {
  let beams = new Map([
    [inputText.indexOf('S'), 1]
  ]);
  const lines = inputText.trimEnd().split('\n');
  for (let y = 1; y < lines.length; y++) {
//     console.debug({ y, beams })
    const nextBeams = new Map();
    for (const [beamHeadX, beamCount] of beams) {
      if (lines[y][beamHeadX] === '.') {
        nextBeams.set(beamHeadX, (nextBeams.get(beamHeadX) ?? 0) + beamCount);
      } else if (lines[y][beamHeadX] === '^') {
        nextBeams.set(beamHeadX + 1, (nextBeams.get(beamHeadX + 1) ?? 0) + beamCount);
        nextBeams.set(beamHeadX - 1, (nextBeams.get(beamHeadX - 1) ?? 0) + beamCount);
      }
    }
    beams = nextBeams;
  }
  return beams.entries().reduce((accu, [_, count]) => accu + count, 0);
}

{
  const start = performance.now();
  const result = part2(document.body.textContent);
  const end = performance.now();
  console.info({
    day: 7,
    part: 2,
    time: end - start,
    result
  })
}