commit 961570ce442e0d98a9fe1e6a1966354d7096ea07
parent 303748ab9224157ee7e752a192a7a9ff96fa167b
Author: Martin Ashby <martin@ashbysoft.com>
Date: Tue, 31 Dec 2024 21:16:04 +0000
Day 10 pt1
Diffstat:
3 files changed, 103 insertions(+), 0 deletions(-)
diff --git a/day10.txt b/day10.txt
@@ -0,0 +1,42 @@
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diff --git a/day10_sample.txt b/day10_sample.txt
@@ -0,0 +1,8 @@
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diff --git a/src/main/java/day10_pt1.java b/src/main/java/day10_pt1.java
@@ -0,0 +1,53 @@
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.io.IOException;
+import java.util.*;
+import java.util.stream.*;
+
+public class day10_pt1 {
+ record Point(int x, int y) {
+ Point add(Vec v) {
+ return new Point(this.x + v.x, this.y + v.y);
+ }
+ }
+ record Vec(int x, int y) {}
+ private static final Vec[] DIRS = new Vec[]{new Vec( 0, 1),
+ new Vec( 1, 0),
+ new Vec( 0,-1),
+ new Vec(-1, 0)};
+ public static void main(String[] args) throws IOException {
+ var grid = Files.readAllLines(Path.of(args[0]));
+ var trailheads = new ArrayList<Point>();
+ var height = grid.size();
+ var width = grid.get(0).length();
+ // pass 1 find trailheads
+ for (int y=0; y<height; y++) {
+ for (int x=0; x<width; x++) {
+ var val = gv(grid, new Point(x, y));
+ if (val == 0) {
+ trailheads.add(new Point(x, y));
+ }
+ }
+ }
+ var res = trailheads.stream().mapToInt(th -> tops(grid, th).size()).sum();
+ System.out.printf("Day 10, pt1: %d\n", res);
+ }
+
+ static Set<Point> tops(List<String> grid, Point p) {
+ var val = gv(grid, p);
+ if (val == 9) {
+ return Set.of(p);
+ } else {
+ return Arrays.stream(DIRS)
+ .filter(d -> gv(grid, p.add(d)) == val+1)
+ .flatMap(d -> tops(grid, p.add(d)).stream())
+ .collect(Collectors.toSet());
+ }
+ }
+
+ static int gv(List<String> grid, Point p) {
+ if (p.y < 0 || p.y >= grid.size()) return -1;
+ if (p.x < 0 || p.x >= grid.get(0).length()) return -1;
+ return grid.get(p.y).charAt(p.x) - '0';
+ }
+}
