Day 8, all in

08/build.zig

@@ -0,0 +1,14 @@
+const Builder = @import("std").build.Builder;
+
+pub fn build(b: *Builder) void {
+    const mode = b.standardReleaseOptions();
+    const exe = b.addExecutable("08", "src/main.zig");
+    exe.setBuildMode(mode);
+    exe.install();
+
+    const run_cmd = exe.run();
+    run_cmd.step.dependOn(b.getInstallStep());
+
+    const run_step = b.step("run", "Run the app");
+    run_step.dependOn(&run_cmd.step);
+}

08/src/main.zig

@@ -0,0 +1,104 @@
+const std = @import("std");
+
+const depth = 100;
+const width = 25;
+const height = 6;
+
+const Layer = [height][width]Colour;
+const Image = [depth]Layer;
+const Colour = enum(u8) {
+    Black = 0,
+    White = 1,
+    Trans = 2,
+};
+
+fn printLayer(l: Layer) void {
+    for (l) |row| {
+        for (row) |byte| {
+            switch (byte) {
+                .Black => {
+                    std.debug.warn(" ");
+                },
+                .White => {
+                    std.debug.warn("*");
+                },
+                else => {
+                    std.debug.warn(" ");
+                },
+            }
+        }
+        std.debug.warn("\n");
+    }
+    std.debug.warn("\n");
+}
+
+fn printImage(image: Image) void {
+    var meta: Layer = undefined;
+    for (meta) |row, y| {
+        for (row) |_, x| {
+            meta[y][x] = .Trans;
+        }
+    }
+
+    for (meta) |*row, y| {
+        for (row) |*b, x| {
+            var z: usize = 0;
+            while (b.* == .Trans) : (z += 1) {
+                if (image[z][y][x] != .Trans) {
+                    b.* = image[z][y][x];
+                }
+            }
+        }
+    }
+
+    printLayer(meta);
+}
+
+pub fn main() anyerror!void {
+    var img: Image = undefined;
+    var zeroCounts = [_]usize{0} ** depth;
+
+    const file = std.io.getStdIn();
+    const stream = &file.inStream().stream;
+
+    for (img) |*layer, z| {
+        for (layer) |*row| {
+            for (row) |*pixel| {
+                var b = try stream.readByte();
+                if (b == '0') zeroCounts[z] += 1;
+                pixel.* = @intToEnum(Colour, b - '0');
+            }
+        }
+    }
+
+    // Now count how many zeroes are in each layer, picking out the smallest
+    var minCount: usize = width * height;
+    var minZ: usize = 0;
+
+    for (zeroCounts) |count, i| {
+        if (count < minCount) {
+            minCount = count;
+            minZ = i;
+        }
+    }
+
+    var num1s: usize = 0;
+    var num2s: usize = 0;
+    for (img[minZ]) |row| {
+        for (row) |b| {
+            switch (b) {
+                .White => {
+                    num1s += 1;
+                },
+                .Trans => {
+                    num2s += 1;
+                },
+                else => {},
+            }
+        }
+    }
+
+    std.debug.warn("Day 8, Part 1: {} with {} zeroes, {} 1s, {} 2s. Result: {}\n\n", minZ, minCount, num1s, num2s, num1s * num2s);
+
+    printImage(img);
+}