day17Part2.ts

import { X_OK } from "constants";
import { isAccessor } from "typescript";

class CubeSpace {
  activeCount = 0;
  potentiallyActive: {
    [key: number]: { x: number; y: number; z: number; w: number };
  } = {};
  memory = new Set<number>();
  getKey(x: number, y: number, z: number, w: number) {
    // big assumption here that we don't go out of range!!!!
    return x * 100 * 100 * 100 + y * 100 * 100 + z * 100 + w;
  }
  getValue(x: number, y: number, z: number, w: number): boolean {
    const key = this.getKey(x, y, z, w);
    return this.memory.has(key);
  }
  setValue(x: number, y: number, z: number, w: number, value: boolean) {
    const key = this.getKey(x, y, z, w);
    this.activeCount++;
    this.memory.add(key);
    // update the potentially active list
    for (let dx = -1; dx <= 1; dx++) {
      for (let dy = -1; dy <= 1; dy++) {
        for (let dz = -1; dz <= 1; dz++) {
          for (let dw = -1; dw <= 1; dw++) {
            this.potentiallyActive[
              this.getKey(x + dx, y + dy, z + dz, w + dw)
            ] = {
              x: x + dx,
              y: y + dy,
              z: z + dz,
              w: w + dw,
            };
          }
        }
      }
    }
  }
}

function day17Part1(input: string) {
  function simulate(cube: CubeSpace): CubeSpace {
    const result = new CubeSpace();
    Object.values(cube.potentiallyActive).forEach((coords) => {
      const { x, y, z, w } = coords;
      let activeNeighbours = 0;
      for (let dx = -1; dx <= 1; dx++) {
        for (let dy = -1; dy <= 1; dy++) {
          for (let dz = -1; dz <= 1; dz++) {
            for (let dw = -1; dw <= 1; dw++) {
              if (dx == 0 && dy == 0 && dz == 0 && dw == 0) {
                continue;
              }
              if (cube.getValue(x + dx, y + dy, z + dz, w + dw)) {
                activeNeighbours++;
              }
            }
          }
        }
      }
      if (cube.getValue(x, y, z, w)) {
        if (activeNeighbours === 2 || activeNeighbours === 3) {
          result.setValue(x, y, z, w, true);
        }
      } else {
        if (activeNeighbours === 3) {
          result.setValue(x, y, z, w, true);
        }
      }
    });
    return result;
  }

  let cube = new CubeSpace();
  input.split("\n").forEach((yRow, y) => {
    yRow.split("").forEach((isActive, x) => {
      cube.setValue(x, y, 0, 0, isActive === "#");
    });
  });
  console.time("day17Part2");
  for (let i = 0; i < 6; i++) {
    cube = simulate(cube);
  }
  console.timeEnd("day17Part2");
  return cube.activeCount;
}
console.log(
  day17Part1(
    `##......
.##...#.
.#######
..###.##
.#.###..
..#.####
##.####.
##..#.##`
  )
);