// Comnbining all ranges (min to max) from each beacon at each level of Y may be fast enough
const fs = require('fs/promises');

const sum = (arr) => arr.reduce((total, num) => total+num, 0);
const arrayOfLength = n => Array.from(Array(n).keys()).map(() => {});

const parseXY = str => str.match(/x=(.*), y=(.*)$/).slice(1).map(x => parseInt(x));

const HEIGHT = 4000000;

const doTouch = (a, b, a2, b2) => {
  const a1 = a - 1;
  const b1 = b + 1;
  if(b1 >= a2 && a1 <= b2) {
    return true;
  }
  return false;
}
const getStartEnd = (x, rad) => [x-rad, x+rad];
const getDistance = (x1, y1, x2, y2) => abs(x1 - x2) + abs(y1 - y2);

const combineTouching = (a,b,c,d) => {
  return [Math.min(a,c), Math.max(b,d)];
}

const abs = x => x < 0 ? x * -1 : x;
const main = async () => {
  const input = (await fs.readFile("./input.txt", 'utf8')).split("\n").slice(0, -1);
  const sets = input.map(row => row.split(": ").map(parseXY));

  const sensors = sets.map(([[sX, sY], [bX, bY]]) => {
    return [sX, sY, getDistance(sX, sY, bX, bY)];
  });

  for(let row = 0; row <= HEIGHT; row++) {
      const coveredArea = sensors.filter(
        ([_, y, rad]) => Math.abs(row-y) <= rad
      ).map(
        ([x, y, rad]) => getStartEnd(x, rad - Math.abs(row - y))
      ).sort(
        (a, b) => a[0] - b[0]
      ).reduce((ranges, [a1, b1]) => {
        if(!ranges) {
          return [[a1, b1]];
        }
        const [a, b] = ranges[ranges.length - 1];
        if(doTouch(a, b, a1, b1)){
          ranges[ranges.length - 1] = combineTouching(a, b, a1, b1);
        } else {
          ranges.push([a1, b1]);
        }
        return ranges;
      }, false);
      if(coveredArea.length > 1) {
        console.log("FOUND IT! Answer: ", (coveredArea[0][1] + 1) * 4000000 + row);
        process.exit();
      }
    if(row % 100000 === 0) {
        console.log("DONE: ", row);
      }
    }
}

main();