Discussion on: Advent of Code 2019 Solution Megathread - Day 3: Crossed Wires

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Woooooo, finally got this one! Took me 2 days, but dangit I solved it on my own and I feel super pleased and relieved. lol

What's lame is I basically had the right idea yesterday, but wasn't adding the absolute value of the coordinates, so was getting the wrong values back and thought my whole solution was wrong. 😒 So I rage deleted everything last night, and rewrote it all today and got it working! 😊

Got to use a set for the first real time, which worked out nicely! I figured I could plot out each coordinate visited by the first wire, and store those in a set (since where a wire crosses itself doesn't matter). Then, for the second wire, I go through and just check to see if the set contains that coordinate already, and if so, store that in it's own array to check over at the end. Ran pretty quickly, though I'm sure I could factor the code to be a bit more function-oriented than I did. Just wanted it to work! lol

Thankfully, part 2 didn't take me all that long...just refactoring my first path run to count the steps taken so far and figure out how/where to store them, then adding it as an extra value onto the end of my crossed points array. Easy! (Ending up reading my coords and counter as a string, so that comparisons were easier to do.)

JavaScript:

let wire1 = input[0].split(',');
let wire2 = input[1].split(','); 

let path1 = new Set();
let path1c = [];
let crosses = [];

let h = 0; 
let v = 0;
let counter = 0;

for (let i = 0; i < wire1.length; i++) {
  let split = [wire1[i].slice(0, 1), wire1[i].slice(1)];
  let dir = split[0];
  let steps = split[1];

  do {
    switch (dir) {
      case 'U':
        v++;
        steps--;
        break;
      case 'D':
        v--;
        steps--;
        break;
      case 'R':
        h++;
        steps--;
        break;
      case 'L':
        h--;
        steps--;
        break;
      }
      counter++;

    if (!path1.has(`${h},${v}`)) {
      path1.add(`${h},${v}`);  
      path1c.push(counter);
    }
  } while  (steps > 0);
}

let setarr = [...path1];

// console.log(path1);

h = 0; 
v = 0;
counter = 0;

for (let i = 0; i < wire2.length; i++) {
  let split = [wire2[i].slice(0, 1), wire2[i].slice(1)];
  let dir = split[0];
  let steps = split[1];

  do {
    switch (dir) {
      case 'U':
        v++;
        steps--;
        break;
      case 'D':
        v--;
        steps--;
        break;
      case 'R':
        h++;
        steps--;
        break;
      case 'L':
        h--;
        steps--;
        break;
      }
      counter++;

    if (path1.has(`${h},${v}`)) {
      let path1pos = setarr.indexOf(`${h},${v}`);
      let path1count = path1c[path1pos];
      let sumsteps = path1count + counter;
      crosses.push(`${h},${v},${sumsteps}`);
    }  
  } while  (steps > 0);
}

// console.log(crosses);

let closest;
let lowest;

crosses.forEach(val => {
  let breakup = val.split(',');
  let valh = breakup[0];
  let valv = breakup[1];
  let valc = breakup[2];

  let distance = Math.abs(valh) + Math.abs(valv);

  if (!closest) {
    closest = distance;
  } else {
    if (distance < closest) {
      closest = distance;
    }
  }

  if (!lowest) {
    lowest = valc;
  } else {
    if (valc < lowest) {
      lowest = valc;
    }
  }
})

console.log(`Part 1: ${closest}`);
console.log(`Part 2: ${lowest}`);