Day14

aoc2023/src/main/java/io/github/zebalu/aoc2023/days/Day14.java

@@ -0,0 +1,191 @@
+package io.github.zebalu.aoc2023.days;
+
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
+import java.util.Comparator;
+import java.util.HashSet;
+import java.util.LinkedHashSet;
+import java.util.List;
+import java.util.SequencedSet;
+import java.util.Set;
+
+public class Day14 {
+    public static void main(String[] args) {
+        String input = readInput();
+        Platform p = new Platform(input);
+        p.tiltNorth();
+        System.out.println(p.loadOnNorth());
+        p.cycle(1_000_000_000);
+        System.out.println(p.loadOnNorth());
+    }
+
+    private static String readInput() {
+        try {
+            return Files.readString(Path.of("day14.txt").toAbsolutePath());
+        } catch (IOException e) {
+            throw new IllegalStateException(e);
+        }
+    }
+
+    private record Coord(int x, int y) {}
+
+    private static class Platform {
+        int width;
+        int height;
+
+        Set<Coord> stoppers = new HashSet<>();
+        Set<Coord> rollers = new HashSet<>();
+
+        Platform(String descS) {
+            List<String> desc = descS.lines().toList();
+            height = desc.size();
+            width = desc.getFirst().length();
+            for(int y=0; y<desc.size(); ++y) {
+                String line = desc.get(y);
+                for(int x=0; x<line.length(); ++x) {
+                    switch (line.charAt(x)) {
+                    case '#' -> stoppers.add(new Coord(x,y));
+                    case 'O' -> rollers.add(new Coord(x,y));
+                    }
+                }
+            }
+        }
+
+        void tiltNorth() {
+            var todo = rollers.stream().sorted(Comparator.comparingInt(Coord::y).thenComparingInt(Coord::x)).toList();
+            todo.stream().forEach(move->{
+                boolean foundBlocker = false;
+                int y = move.y;
+                Coord target = null;
+                while(y>0 && !foundBlocker) {
+                    --y;
+                    Coord next = new Coord(move.x, y);
+                    foundBlocker = stoppers.contains(next) || rollers.contains(next);
+                    if(!foundBlocker) {
+                        target = next;
+                    }
+                }
+                if(target != null) {
+                    rollers.remove(move);
+                    rollers.add(target);
+                }
+            });
+        }
+
+        void tiltSouth() {
+            var todo = rollers.stream().sorted(Comparator.comparingInt(Coord::y).reversed().thenComparingInt(Coord::x)).toList();
+            todo.stream().forEach(move->{
+                boolean foundBlocker = false;
+                int y = move.y;
+                Coord target = null;
+                while(y<height-1 && !foundBlocker) {
+                    ++y;
+                    Coord next = new Coord(move.x, y);
+                    foundBlocker = stoppers.contains(next) || rollers.contains(next);
+                    if(!foundBlocker) {
+                        target = next;
+                    }
+                }
+                if(target != null) {
+                    rollers.remove(move);
+                    rollers.add(target);
+                }
+            });
+        }
+
+        void titlWest() {
+            var todo = rollers.stream().sorted(Comparator.comparingInt(Coord::x).thenComparingInt(Coord::y)).toList();
+            todo.stream().forEach(move->{
+                boolean foundBlocker = false;
+                int x = move.x;
+                Coord target = null;
+                while(x>0 && !foundBlocker) {
+                    --x;
+                    Coord next = new Coord(x, move.y);
+                    foundBlocker = stoppers.contains(next) || rollers.contains(next);
+                    if(!foundBlocker) {
+                        target = next;
+                    }
+                }
+                if(target != null) {
+                    rollers.remove(move);
+                    rollers.add(target);
+                }
+            });
+        }
+
+        void tiltEast() {
+            var todo = rollers.stream().sorted(Comparator.comparingInt(Coord::x).reversed().thenComparingInt(Coord::y)).toList();
+            todo.stream().forEach(move->{
+                boolean foundBlocker = false;
+                int x = move.x;
+                Coord target = null;
+                while(x<width-1 && !foundBlocker) {
+                    ++x;
+                    Coord next = new Coord(x, move.y);
+                    foundBlocker = stoppers.contains(next) || rollers.contains(next);
+                    if(!foundBlocker) {
+                        target = next;
+                    }
+                }
+                if(target != null) {
+                    rollers.remove(move);
+                    rollers.add(target);
+                }
+            });
+        }
+
+        void cycle() {
+            tiltNorth();
+            titlWest();
+            tiltSouth();
+            tiltEast();
+        }
+
+        void cycle(int times) {
+            int steps = 1;
+            cycle();
+            SequencedSet<Set<Coord>> history = new LinkedHashSet<>();
+            while(!history.contains(rollers)) {
+                history.add(new HashSet<>(rollers));
+                cycle();
+                ++steps;
+            }
+            int length = 0;
+            var iterator = history.reversed().iterator();
+            boolean found = false;
+            while(iterator.hasNext() && !found) {
+                var value = iterator.next();
+                ++length;
+                found = value.equals(rollers);
+            }
+            int remaining = (times - steps) % length;
+            for(int i=0; i<remaining; ++i) {
+                cycle();
+            }
+        }
+
+        int loadOnNorth() {
+            return rollers.stream().sorted(Comparator.comparingInt(Coord::y).thenComparingInt(Coord::x)).mapToInt(c->height-c.y).sum();
+        }
+        @Override
+        public String toString() {
+            StringBuilder sb = new StringBuilder();
+            for(int y=0; y<height; ++y) {
+                for(int x=0; x<width; ++x) {
+                    Coord c=new Coord(x,y);
+                    if(stoppers.contains(c)) {
+                        sb.append('#');
+                    } else if(rollers.contains(c)) {
+                        sb.append('O');
+                    } else {
+                        sb.append('.');
+                    }
+                }
+                sb.append('\n');
+            }
+            return sb.toString();
+        }
+    }
+}

aoc2023/src/main/java/io/github/zebalu/aoc2023/main/App.java

@@ -25,6 +25,7 @@
 import io.github.zebalu.aoc2023.days.Day11;
 import io.github.zebalu.aoc2023.days.Day12;
 import io.github.zebalu.aoc2023.days.Day13;
+import io.github.zebalu.aoc2023.days.Day14;
 
 public class App {
 
@@ -53,6 +54,7 @@ public static void main(String[] args) {
         exec(new DisplayData(11, "Cosmic Expansion", Day11::main));
         exec(new DisplayData(12, "Hot Springs", Day12::main));
         exec(new DisplayData(13, "Point of Incidence", Day13::main));
+        exec(new DisplayData(14, "Parabolic Reflector Dish", Day14::main));
         Instant end = Instant.now();
         System.out.println("so far:\t"+Duration.between(start, end).toMillis()+" ms...");
     }