advent-of-code/2022/9/index2.js

const fs = require('fs/promises');

const tailVisited = {'0~0': true};

const rope = [[0,0], [0,0], [0,0], [0,0], [0,0], [0,0], [0,0], [0,0], [0,0], [0,0]];

const keypress = async () => {
  process.stdin.setRawMode(true)
  return new Promise(resolve => process.stdin.once('data', data => {
    const byteArray = [...data]
    if (byteArray.length > 0 && byteArray[0] === 3) {
      console.log('^C')
      process.exit(1)
    }
    process.stdin.setRawMode(false)
    resolve()
  }))
}

const moveRope = (direction) => {
  const lastSpot = [rope[0][0], rope[0][1]];
  switch (direction) {
    case "R":
      rope[0][0] += 1;
      break;
    case "L":
      rope[0][0] -= 1;
      break;
    case "U":
      rope[0][1] -= 1;
      break;
    case "D":
      rope[0][1] += 1;
      break;
  }
  for(let i = 1; i < rope.length; ++i) {
    rope[i] = moveSeg(rope[i], i)
  }
}

const moveSeg = ([x, y], i) =>  {
  if(i === rope.length) return;
  const seg = rope[i - 1];
  //console.log("uhh: ", rope, " ", i, " ", seg);
  const [lx, ly] = seg;
    V= rope[i - 1];
  if(lx === x) {
    if(ly === y + 2) {
      return [x, y + 1];
    }
    if(ly === y - 2) {
      return[x, y - 1];
    }
  }
  if(ly === y) {
    if(lx === x + 2) {
      return [x + 1, y];
    }
    if(lx === x - 2) {
      return rope[i] = [x - 1, y];
    }
  }
  if(Math.max(Math.abs(x - lx), Math.abs(y - ly)) > 1) {
    const xDiff = lx - x;
    const yDiff = ly - y;
    if(xDiff === 0 || yDiff === 0) {
      console.log([x, y, lx, ly])
      console.log("ROPE: ", rope);
    }
    return [x + xDiff/Math.abs(xDiff), y + yDiff/Math.abs(yDiff)];
  }

  return [x, y];
}

const printGraph = () => {
  console.log("\n");
  console.log(rope);
  console.log("\n");
  for(let y = -15; y <= 15; y++) {
    const row = ["·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·",
      "·", "·", "·", "·", "·", "·"].map((spot, i) => {
        const x = i - 15;
        const [hx, hy] = rope[0];
        const [tx, ty] = rope[9];
        let ch = "·";
        if(!(y % 5) && !(x % 5)) {
          ch = "▪";
        }
        if(y === 0 && x === 0) {
          ch = "0";
        }
        if(y === ty && x === tx) {
          ch = "T";
        }
        rope.slice(0, -1).reverse().forEach(([a, b], j) => {
          if(a === x && b === y) {
            ch = j+1;
          }
        });
        if(y === hy && x === hx) {
          ch = "H";
        }
        return ch;
      });
    console.log(row.join(""));
  }
  console.log("\n\n");
};

(async () => {
  const input = await fs.readFile("./input.txt", 'utf8');

  const lines = input.split("\n").map(t => t.split(" "));

  //printGraph();
  for (const [direction, times] of lines) {
    for(let i = 0; i < times; ++i) {
      //await keypress();
      console.log("Moving ", direction);
      moveRope(direction);
      //printGraph();
      tailVisited[`${rope[9][0]}~${rope[9][1]}`] = true;

    }
  }
      console.log(tailVisited);

  console.log(Object.values(tailVisited).length);
})();