aoc2024

commit f89b18893aa320fc76f036d542aea31bb12b3fd7
parent efd500459462d87f5df89c3b0479a5356f8aa90d
Author: Martin Ashby <martin@ashbysoft.com>
Date:   Thu,  2 Jan 2025 21:44:20 +0000

Day 14 pt2

Diffstat:
A
src/main/java/day14_pt2.java
 | 
72
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

1 file changed, 72 insertions(+), 0 deletions(-)
diff --git a/src/main/java/day14_pt2.java b/src/main/java/day14_pt2.java
@@ -0,0 +1,72 @@
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.io.IOException;
+import java.util.*;
+import java.util.stream.*;
+import java.util.regex.*;
+
+class day14_pt2 {
+  static final Pattern P = Pattern.compile("p=(-?\\d+),(-?\\d+) v=(-?\\d+),(-?\\d+)");
+  record Point(int x, int y) {
+    Point add(Vec v, int width, int height) {
+      var nx = (this.x + v.x) % width;
+      if (nx < 0) {
+        nx += width;
+      }
+      var ny = (this.y + v.y) % height;
+      if (ny < 0) {
+        ny += height;
+      }
+      return new Point(nx, ny);
+    }
+  }
+  record Vec(int x, int y) {}
+  record Robot(int label, Vec velocity) {}
+  public static void main(String[] args) throws IOException, InterruptedException {
+    var lines = Files.readAllLines(Path.of(args[0]));
+    var width = 101;
+    var height = 103;
+    var robots = new ArrayList<Robot>();
+    var positions = new ArrayList<Point>();
+    for (var ix=0; ix<lines.size(); ix++) {
+      var line = lines.get(ix);
+      var m = P.matcher(line);
+      if (!m.matches()) throw new RuntimeException("line didn't match [%s]".formatted(line));
+      var px = Integer.parseInt(m.group(1));
+      var py = Integer.parseInt(m.group(2));
+      var dx = Integer.parseInt(m.group(3));
+      var dy = Integer.parseInt(m.group(4));
+      robots.add(new Robot(ix, new Vec(dx, dy)));
+      positions.add(new Point(px, py));
+    }
+    // System.out.println(robots);
+    // System.out.println(positions);
+    for (var secs = 0; true; secs++) {
+      for (var ix=0; ix<robots.size(); ix++) {
+        var robot = robots.get(ix);
+        var p = positions.get(ix);
+        var p2 = p.add(robot.velocity, width, height);
+        positions.set(ix, p2);
+      }
+      //Thread.sleep(300);
+      var cts = positions.stream().collect(Collectors.toMap(p -> p, p -> 1, (i1, i2) -> i1 + i2));
+      // debug
+      if (cts.values().stream().allMatch(x -> x == 1)) {
+        System.out.printf("secs: %d\n", secs+1);
+        for (var y=0; y<height; y++) {
+          for (var x=0; x<width; x++) {
+            var ct = cts.get(new Point(x, y));
+            if (ct != null) {
+              System.out.printf("%d", ct);
+            } else {
+              System.out.print(".");
+            }
+          }
+          System.out.print("\n");
+        }
+        System.out.printf("Day 14 pt1: %d\n", secs+1);
+        break;
+      }
+    }
+  }
+}