1 files changed, 67 insertions, 0 deletions
diff --git a/src/12/main.zig b/src/12/main.zig
new file mode 100644
index 0000000..12fd5f0
--- /dev/null
+++ b/src/12/main.zig
@@ -0,0 +1,67 @@
+const std = @import("std");
+const aoc = @import("aoc");
+const Pos = aoc.Pos;
+const Dir = aoc.Dir;
+
+const Ship = struct { pos: Pos, waypoint: Pos, dir: usize };
+
+fn part1(allocator: std.mem.Allocator, input: []u8, args: [][]u8) !?[]u8 {
+    _ = args;
+
+    var ship = Ship{ .pos = Pos{ .x = 0, .y = 0 }, .waypoint = Pos{ .x = 0, .y = 0 }, .dir = 0 };
+    var lineit = std.mem.tokenize(u8, input, "\n");
+    while (lineit.next()) |line| {
+        const val = try std.fmt.parseInt(u32, line[1..], 10);
+        switch (line[0]) {
+            'N' => ship.pos = ship.pos.add(Dir.North.mult(val)),
+            'S' => ship.pos = ship.pos.add(Dir.South.mult(val)),
+            'E' => ship.pos = ship.pos.add(Dir.East.mult(val)),
+            'W' => ship.pos = ship.pos.add(Dir.West.mult(val)),
+            'L' => ship.dir = Dir.nextCCW(ship.dir, @divExact(val, 90)),
+            'R' => ship.dir = Dir.nextCW(ship.dir, @divExact(val, 90)),
+            'F' => ship.pos = ship.pos.add(Dir.dirs[ship.dir].mult(val)),
+            else => {
+                return aoc.Error.InvalidInput;
+            },
+        }
+    }
+
+    const answer = std.math.absCast(ship.pos.x) + std.math.absCast(ship.pos.y);
+
+    return try std.fmt.allocPrint(allocator, "{d}", .{answer});
+}
+
+fn part2(allocator: std.mem.Allocator, input: []u8, args: [][]u8) !?[]u8 {
+    _ = args;
+
+    var ship = Ship{ .pos = Pos{ .x = 0, .y = 0 }, .waypoint = Pos{ .x = 10, .y = 1 }, .dir = 0 };
+    var lineit = std.mem.tokenize(u8, input, "\n");
+    while (lineit.next()) |line| {
+        const val = try std.fmt.parseInt(u32, line[1..], 10);
+        switch (line[0]) {
+            'N' => ship.waypoint = ship.waypoint.add(Dir.North.mult(val)),
+            'S' => ship.waypoint = ship.waypoint.add(Dir.South.mult(val)),
+            'E' => ship.waypoint = ship.waypoint.add(Dir.East.mult(val)),
+            'W' => ship.waypoint = ship.waypoint.add(Dir.West.mult(val)),
+            'L' => {
+                var new = Dir.rotCCW(ship.waypoint, @divExact(val, 90));
+                ship.waypoint = new;
+            },
+            'R' => {
+                var new = Dir.rotCW(ship.waypoint, @divExact(val, 90));
+                ship.waypoint = new;
+            },
+            'F' => ship.pos = ship.pos.add(ship.waypoint.mult(val)),
+            else => {
+                return aoc.Error.InvalidInput;
+            },
+        }
+        aoc.debugfmt("{s} {} {} {} {}\n", .{ line, ship.waypoint.x, ship.waypoint.y, ship.pos.x, ship.pos.y });
+    }
+
+    const answer = std.math.absCast(ship.pos.x) + std.math.absCast(ship.pos.y);
+
+    return try std.fmt.allocPrint(allocator, "{d}", .{answer});
+}
+
+pub const main = aoc.main(part1, part2, .{ "1191", "61053" });