Day 8

l0s · l0s · commit a685df3bf0cd · 2022-12-07T21:38:18.000-08:00
diff --git a/src/test/java/com/macasaet/Day08.java b/src/test/java/com/macasaet/Day08.java
@@ -0,0 +1,161 @@
+package com.macasaet;
+
+import org.junit.jupiter.api.Test;
+
+import java.util.stream.Collectors;
+import java.util.stream.StreamSupport;
+
+/**
+ * --- Day 8: Treetop Tree House ---
+ * <a href="https://adventofcode.com/2022/day/8">https://adventofcode.com/2022/day/8</a>
+ */
+public class Day08 {
+
+    record Forest(int[][] grid) {
+        public int countVisible() {
+            int result = 0;
+            for(int i = grid().length; --i >= 0; ) {
+                final var row = grid()[i];
+                for(int j = row.length; --j >= 0; ) {
+                    if(isVisible(i, j)) {
+                        result++;
+                    }
+                }
+            }
+            return result;
+        }
+
+        public int scenicScore(final int x, final int y) {
+            final int treeHeight = grid()[x][y];
+            int northScore = 0;
+            for(int i = x; --i >= 0; ) {
+                final var height = grid()[i][y];
+                northScore += 1;
+                if(height >= treeHeight) {
+                    break;
+                }
+            }
+            int southScore = 0;
+            for(int i = x + 1; i < grid().length; i++) {
+                final var height = grid()[i][y];
+                southScore += 1;
+                if(height >= treeHeight) {
+                    break;
+                }
+            }
+            int westScore = 0;
+            for(int j = y; --j >= 0; ) {
+                final var height = grid()[x][j];
+                westScore += 1;
+                if(height >= treeHeight) {
+                    break;
+                }
+            }
+            int eastScore = 0;
+            for(int j = y + 1; j < grid()[x].length; j++) {
+                final var height = grid()[x][j];
+                eastScore += 1;
+                if(height >= treeHeight) {
+                    break;
+                }
+            }
+            return northScore * eastScore * southScore * westScore;
+        }
+
+        boolean isVisible(final int x, final int y) {
+            if(x == 0 || x == grid().length || y == 0 || y == grid()[x].length) {
+                // trees on the edge
+                return true;
+            }
+            final int treeHeight = grid()[x][y];
+            if (!isObstructedFromTheNorth(x, y, treeHeight)) {
+                return true;
+            }
+            if (!isObstructedFromTheSouth(x, y, treeHeight)) {
+                return true;
+            }
+            if (!isObstructedFromTheWest(x, y, treeHeight)) {
+                return true;
+            }
+            if (!isObstructedFromTheEast(x, y, treeHeight)) {
+                return true;
+            }
+            return false;
+        }
+
+        private boolean isObstructedFromTheEast(int x, int y, int treeHeight) {
+            for(int j = grid()[x].length; --j > y; ) {
+                if(grid()[x][j] >= treeHeight) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        private boolean isObstructedFromTheWest(int x, int y, int treeHeight) {
+            for(int j = y; --j >= 0; ) {
+                if(grid()[x][j] >= treeHeight) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        private boolean isObstructedFromTheSouth(int x, int y, int treeHeight) {
+            for(int i = grid().length; --i > x; ) {
+                if(grid()[i][y] >= treeHeight) {
+                    return true;
+                }
+            }
+            return false;
+        }
+
+        private boolean isObstructedFromTheNorth(int x, int y, int treeHeight) {
+            for(int i = x; --i >= 0; ) {
+                if(grid()[i][y] >= treeHeight) {
+                    return true;
+                }
+            }
+            return false;
+        }
+    }
+
+    protected Forest getInput() {
+        final var list = StreamSupport
+                .stream(new LineSpliterator("day-08.txt"),
+                        false)
+                .map(line -> {
+                    final var chars = line.toCharArray();
+                    final var row = new int[chars.length];
+                    for(int i = chars.length; --i >= 0; row[i] = chars[i] - '0');
+                    return row;
+                })
+                .collect(Collectors.toList());
+        final var grid = new int[list.size()][];
+        for(int i = list.size(); --i >= 0; grid[i] = list.get(i));
+        return new Forest(grid);
+    }
+
+    @Test
+    public final void part1() {
+        final var forest = getInput();
+        final var result = forest.countVisible();
+        System.out.println("Part 1: " + result);
+    }
+
+    @Test
+    public final void part2() {
+        final var forest = getInput();
+        int result = Integer.MIN_VALUE;
+        for(int i = forest.grid().length; --i >= 0; ) {
+            for( int j = forest.grid.length; --j >= 0; ) {
+                final var score = forest.scenicScore(i, j);
+                if(score > result) {
+                    result = score;
+                }
+            }
+        }
+        System.out.println("Part 2: " + result);
+    }
+
+}
diff --git a/src/test/resources/sample/day-08.txt b/src/test/resources/sample/day-08.txt
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+30373
+25512
+65332
+33549
+35390

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