2024 q7

Author: icecreamhead

twentytwentyfour/src/main/java/com/icecreamhead/adventofcode/q6/GuardGallivant.java

@@ -1,6 +1,5 @@
 package com.icecreamhead.adventofcode.q6;
 
-import java.io.IOException;
 import java.util.ArrayList;
 import java.util.HashSet;
 import java.util.Set;
@@ -95,7 +94,7 @@ long pt2(char[][] map) {
           x = nextx;
           y = nexty;
           been.add(new P(g, x, y));
-          if (newPathIntersectsExistingPath(been, map, rotate90(g), x, y)) {
+          if (newPathIntersectsExistingPath(been, map, rotate90(g), x, y, false)) {
             switch (g) {
               case UP -> blocks.add(new P('O', x, y - 1));
               case RIGHT -> blocks.add(new P('O', x + 1, y));
@@ -120,11 +119,18 @@ long pt2(char[][] map) {
     return blocks.size();
   }
 
-  private static boolean newPathIntersectsExistingPath(Set<P> been, char[][] map, char g, int x, int y) {
+  private static boolean newPathIntersectsExistingPath(Set<P> been, char[][] map, char g, int x, int y, boolean alreadyRecursed) {
     while (true) {
 //      print(map, g, x, y);
+
       try {
-        if (map[y][x] == '#') return false; // need to recurse here
+        if (map[y][x] == '#' && !alreadyRecursed) return switch (g) {
+          case UP -> newPathIntersectsExistingPath(been, map, rotate90(g), x, y + 1, true);
+          case DOWN -> newPathIntersectsExistingPath(been, map, rotate90(g), x, y - 1, true);
+          case LEFT -> newPathIntersectsExistingPath(been, map, rotate90(g), x + 1, y, true);
+          case RIGHT -> newPathIntersectsExistingPath(been, map, rotate90(g), x - 1, y, true);
+          default -> throw new IllegalStateException("Illegal g: " + g);
+        };
       } catch (ArrayIndexOutOfBoundsException e) {
 //        System.err.println(e);
         return false;

twentytwentyfour/src/main/java/com/icecreamhead/adventofcode/q7/BridgeRepair.java

@@ -0,0 +1,51 @@
+package com.icecreamhead.adventofcode.q7;
+
+import java.util.Arrays;
+import java.util.List;
+import java.util.Set;
+import java.util.function.BiFunction;
+import java.util.stream.Stream;
+
+public class BridgeRepair {
+
+    long pt1(List<String> input) {
+        var ops = Set.of(add, mul);
+        return input.stream()
+                .mapToLong(l -> {
+                    long expected = Long.parseLong(l.split(":")[0].strip());
+                    long[] vs = Arrays.stream(l.split(":")[1].strip().split(" ")).mapToLong(Long::parseLong).toArray();
+                    if (ops.stream().anyMatch(o -> recursiveFind(o, vs[0], vs[1], vs, 2, expected, ops))) {
+                        return expected;
+                    }
+                    return 0;
+                })
+                .sum();
+    }
+
+    long pt2(List<String> input) {
+        var ops = Set.of(add, mul, cat);
+        return input.stream()
+                .mapToLong(l -> {
+                    long expected = Long.parseLong(l.split(":")[0].strip());
+                    long[] vs = Arrays.stream(l.split(":")[1].strip().split(" ")).mapToLong(Long::parseLong).toArray();
+                    if (ops.stream().anyMatch(o -> recursiveFind(o, vs[0], vs[1], vs, 2, expected, ops))) {
+                        return expected;
+                    }
+                    return 0;
+                })
+                .sum();
+    }
+
+    private boolean recursiveFind(BiFunction<Long, Long, Long> op, long x, long y, long[] tail, int nextIdx, long expected, Set<BiFunction<Long, Long, Long>> ops) {
+        long z = op.apply(x, y);
+        if (z > expected) return false;
+        if (nextIdx == tail.length) {
+            return z == expected;
+        }
+        return ops.stream().anyMatch(o -> recursiveFind(o, z, tail[nextIdx], tail, nextIdx + 1, expected, ops));
+    }
+
+    private static final BiFunction<Long, Long, Long> add = Long::sum;
+    private static final BiFunction<Long, Long, Long> mul = (Long x, Long y) -> x * y;
+    private static final BiFunction<Long, Long, Long> cat = (Long x, Long y) -> Long.parseLong("" + x + y);
+}

twentytwentyfour/src/main/resources/q6/sample2.txt

@@ -0,0 +1,6 @@
+.#....
+....#.
+#^....
+......
+......
+...#..