Solve day 8 part 2

src/day08.zig

@@ -11,18 +11,32 @@ const MAX_Y = 99;
 
 const Grid = struct {
     grid: [MAX_Y][MAX_X]u8,
+    size: usize,
     fn new() Grid {
         return Grid{
             .grid = [_][MAX_X]u8{[_]u8{0} ** MAX_X} ** MAX_Y,
+            .size = MAX_Y,
         };
     }
-    fn is_tree_visible(self: Grid, size: usize, x: usize, y: usize) bool {
+    fn parse(data: []const u8) !Grid {
+        var grid = Grid.new();
+        var lines = std.mem.tokenize(u8, data, "\n");
+        var y: usize = 0;
+        while (lines.next()) |line| : (y += 1) {
+            var x: usize = 0;
+            grid.size = line.len;
+            while (x < line.len) : (x += 1) {
+                const height = try std.fmt.parseInt(u8, line[x .. x + 1], 10);
+                grid.grid[y][x] = height;
+            }
+        }
+        return grid;
+    }
+    fn is_tree_visible(self: Grid, x: usize, y: usize) bool {
         const height = self.grid[y][x];
-        // std.debug.print("testing: {d}, {d}: {d}\n", .{ x, y, height });
         var up_y = y - 1;
         while (true) : (up_y -= 1) {
             if (self.grid[up_y][x] >= height) {
-                // std.debug.print("up_y fail: {d}, {d}: {d}\n", .{ x, up_y, height });
                 break;
             }
             if (up_y == 0) return true;
@@ -30,53 +44,64 @@ const Grid = struct {
         var left_x = x - 1;
         while (true) : (left_x -= 1) {
             if (self.grid[y][left_x] >= height) {
-                // std.debug.print("left_x fail: {d}, {d}: {d}\n", .{ left_x, y, height });
                 break;
             }
             if (left_x == 0) return true;
         }
         var down_y = y + 1;
-        while (down_y < size) : (down_y += 1) {
+        while (down_y < self.size) : (down_y += 1) {
             if (self.grid[down_y][x] >= height) {
-                // std.debug.print("down_y fail: {d}, {d}: {d}\n", .{ x, down_y, height });
                 break;
             }
-            if (down_y == size - 1) return true;
+            if (down_y == self.size - 1) return true;
         }
         var right_x = x + 1;
-        while (right_x < size) : (right_x += 1) {
+        while (right_x < self.size) : (right_x += 1) {
             if (self.grid[y][right_x] >= height) {
-                // std.debug.print("right_x fail: {d}, {d}: {d}\n", .{ right_x, y, height });
                 break;
             }
-            if (right_x == size - 1) return true;
+            if (right_x == self.size - 1) return true;
         }
         return false;
     }
+    fn tree_score(self: Grid, x: usize, y: usize) usize {
+        const height = self.grid[y][x];
+        var up_y: usize = 1;
+        while (y - up_y > 0) : (up_y += 1) {
+            if (self.grid[y - up_y][x] >= height) {
+                break;
+            }
+        }
+        var left_x: usize = 1;
+        while (x - left_x > 0) : (left_x += 1) {
+            if (self.grid[y][x - left_x] >= height) {
+                break;
+            }
+        }
+        var down_y: usize = 1;
+        while (y + down_y < self.size - 1) : (down_y += 1) {
+            if (self.grid[y + down_y][x] >= height) {
+                break;
+            }
+        }
+        var right_x: usize = 1;
+        while (x + right_x < self.size - 1) : (right_x += 1) {
+            if (self.grid[y][x + right_x] >= height) {
+                break;
+            }
+        }
+        return up_y * left_x * down_y * right_x;
+    }
 };
 
 pub fn solve_part1(data: []const u8) !usize {
-    var lines = std.mem.tokenize(u8, data, "\n");
-    var grid = Grid.new();
-    var size: usize = 0;
-    var y: usize = 0;
-    while (lines.next()) |line| : (y += 1) {
-        var x: usize = 0;
-        size = line.len;
-        std.debug.print("line.len: {d}\n", .{line.len});
-        while (x < line.len) : (x += 1) {
-            const height = try std.fmt.parseInt(u8, line[x .. x + 1], 10);
-            grid.grid[y][x] = height;
-        }
-    }
-
-    var count: usize = (size * 4) - 4;
-    std.debug.print("count: {d}\n", .{count});
-    y = 1;
-    while (y < size - 1) : (y += 1) {
+    var grid = try Grid.parse(data);
+    var count: usize = (grid.size * 4) - 4;
+    var y: usize = 1;
+    while (y < grid.size - 1) : (y += 1) {
         var x: usize = 1;
-        while (x < size - 1) : (x += 1) {
-            if (grid.is_tree_visible(size, x, y)) {
+        while (x < grid.size - 1) : (x += 1) {
+            if (grid.is_tree_visible(x, y)) {
                 count += 1;
             }
         }
@@ -85,9 +110,19 @@ pub fn solve_part1(data: []const u8) !usize {
 }
 
 pub fn solve_part2(data: []const u8) !usize {
-    var lines = std.mem.tokenize(u8, data, "\n");
-    _ = lines;
-    return 0;
+    var grid = try Grid.parse(data);
+    var best_score: usize = 0;
+    var y: usize = 1;
+    while (y < grid.size - 1) : (y += 1) {
+        var x: usize = 1;
+        while (x < grid.size - 1) : (x += 1) {
+            const score = grid.tree_score(x, y);
+            if (score > best_score) {
+                best_score = score;
+            }
+        }
+    }
+    return best_score;
 }
 
 test "solves part1" {
@@ -95,5 +130,5 @@ test "solves part1" {
 }
 
 test "solves part2" {
-    try std.testing.expectEqual(solve_part2(test_input1), 0);
+    try std.testing.expectEqual(solve_part2(test_input1), 8);
 }