AoC 2024 Day 4 - Java

package aoc2024;

import java.util.List;

import aoc2024.ak.CharGrid;
import aoc2024.ak.Fn;
import aoc2024.ak.I1m;
import aoc2024.ak.I2;
import aoc2024.ak.I2m;

public class D4 {

  public static void main(String... args) {
    CharGrid grid = Fn.inputLinesTrimmedAsCharGrid("d4.txt");
    { // p1
      I1m p1 = new I1m(0);
      List<I2> velocities = List.of(
        new I2(1, 0),
        new I2(-1, 0),
        new I2(0, -1),
        new I2(0, 1),
        new I2(1, 1),
        new I2(1, -1),
        new I2(-1, 1),
        new I2(-1, -1)
      );
      String target = "XMAS";
      // on each grid-slot, send out our probes
      grid.scan(p1, (c, g, x, y, v) -> {
        PROBE:
        for (I2 velocity : velocities) {
          Probe probe = new Probe(x, y, velocity);
          // move the probe, checking for our desired characters
          for (int i = 0; i < target.length(); i++) {
            char t = target.charAt(i);
            if (!g.check(probe.position.x(), probe.position.y(), t)) { continue PROBE; }
            probe.position.add(probe.velocity);
          }
          c.x += 1;
        }
        return true;
      });
      System.out.println("p1: " + p1.x);
    }
    { // p2
      I1m p2 = new I1m(0);
      List<Probe.Spawn> spawns = List.of(
        new Probe.Spawn(new I2(-1, -1), new I2(1, 1)),
        new Probe.Spawn(new I2(-1, 1), new I2(1, -1)),
        new Probe.Spawn(new I2(1, -1), new I2(-1, 1)),
        new Probe.Spawn(new I2(1, 1), new I2(-1, -1))
      );
      String target = "MAS";
      // on each grid-slot, send out our probes
      grid.scan(p2, (c, g, x, y, v) -> {
        int n = 0;
        PROBE:
        for (Probe.Spawn spawn : spawns) {
          Probe probe = new Probe(x + spawn.offset.x(), y + spawn.offset.y(), spawn.velocity);
          // move the probe, checking for our desired characters
          for (int i = 0; i < target.length(); i++) {
            char t = target.charAt(i);
            if (!g.check(probe.position.x(), probe.position.y(), t)) { continue PROBE; }
            probe.position.add(probe.velocity);
          }
          n += 1;
        }
        if (n >= 2) { c.x += 1; }
        return true;
      });
      System.out.println("p2: " + p2.x);
    }
  }

  public static class Probe {
    public final I2m position;
    public final I2 velocity;

    public Probe (int x, int y, I2 velocity) {
      position = new I2m(x, y);
      this.velocity = velocity;
    }

    public static record Spawn (I2 offset, I2 velocity) {}
  }

  /* ~~~~~~~~~~
   *  CharGrid
   * ~~~~~~~~~~
   * public <C> void scan (C context, Scanner<C> scanner) {
   *   SCAN:
   *   for (int y = 0; y < rows; y++) {
   *     for (int x = 0; x < columns; x++) {
   *       boolean _continue = scanner.visit(context, this, x, y, get(x, y));
   *       if (!_continue) { break SCAN; }
   *     }
   *   }
   * }
   *
   * public boolean check (int x, int y, char v) {
   *   if (!withinBounds(x, y)) { return false; }
   *   return get(x, y) == v;
   * }
   */

}