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| Original file line number | Diff line number | Diff line change |
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| const std = @import("std"); | ||
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| pub fn build(b: *std.Build) void { | ||
| const target = b.standardTargetOptions(.{}); | ||
| const optimize = b.standardOptimizeOption(.{}); | ||
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| const utils = b.dependency("utils", .{ .target = target, .optimize = optimize }).module("utils"); | ||
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| const exe = b.addExecutable(.{ | ||
| .name = "day4", | ||
| .root_source_file = b.path("solve.zig"), | ||
| .target = target, | ||
| .optimize = optimize, | ||
| }); | ||
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| exe.root_module.addImport("utils", utils); | ||
| b.installArtifact(exe); | ||
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| { // Run | ||
| const run_step = b.step("run", "Run the app"); | ||
| const run_cmd = b.addRunArtifact(exe); | ||
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| run_cmd.step.dependOn(b.getInstallStep()); | ||
| if (b.args) |args| { | ||
| run_cmd.addArgs(args); | ||
| } | ||
| run_step.dependOn(&run_cmd.step); | ||
| } | ||
| { // Test | ||
| const test_step = b.step("test", "Run unit tests"); | ||
| const unit_tests = b.addTest(.{ | ||
| .root_source_file = b.path("solve.zig"), | ||
| .target = target, | ||
| .optimize = optimize, | ||
| }); | ||
| const run_unit_tests = b.addRunArtifact(unit_tests); | ||
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| unit_tests.root_module.addImport("utils", utils); | ||
| test_step.dependOn(&run_unit_tests.step); | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,11 @@ | ||
| .{ | ||
| .name = "day04", | ||
| .version = "0.1.0", | ||
| .dependencies = .{ | ||
| .utils = .{ | ||
| .url = "../utils/", | ||
| .hash = "122059863bba3b73097c2905eacfa772e5c9ad7cd6616270b08dfdf41e3d81900420", | ||
| }, | ||
| }, | ||
| .paths = .{ "build.zig", "build.zig.zon", "solve.zig" }, | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,160 @@ | ||
| const std = @import("std"); | ||
| const utils = @import("utils"); | ||
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| const PositionedLetter = std.AutoHashMap(Point, u8); | ||
| const Allocator = std.mem.Allocator; | ||
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| const Point = struct { | ||
| x: i32, | ||
| y: i32, | ||
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| pub fn add(self: Point, other: Point) Point { | ||
| return .{ .x = self.x + other.x, .y = self.y + other.y }; | ||
| } | ||
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| pub fn corners(self: Point) CornerIterator { | ||
| return .{ .center = self }; | ||
| } | ||
| }; | ||
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| /// Loop over the 8 possible directions | ||
| const directions: [8]Point = blk: { | ||
| var result: [8]Point = undefined; | ||
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| for (0..9) |i| { | ||
| result[i - (if (i > 4) 1 else 0)] = .{ .x = (@as(i32, i) % 3) - 1, .y = @as(i32, i) / 3 - 1 }; | ||
| } | ||
| break :blk result; | ||
| }; | ||
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| /// Infinite iteration from a point in a given direction | ||
| const RayIterator = struct { | ||
| current: Point, | ||
| move: Point, | ||
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| pub fn next(self: *RayIterator) ?Point { | ||
| self.current = self.current.add(self.move); | ||
| return self.current; | ||
| } | ||
| }; | ||
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| /// Iterate over the 4 corners of a given point | ||
| const CornerIterator = struct { | ||
| center: Point, | ||
| index: u8 = 0, | ||
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| const corners: [4]Point = .{ | ||
| .{ .x = -1, .y = -1 }, | ||
| .{ .x = 1, .y = -1 }, | ||
| .{ .x = 1, .y = 1 }, | ||
| .{ .x = -1, .y = 1 }, | ||
| }; | ||
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| pub fn next(self: *CornerIterator) ?Point { | ||
| if (self.index == 4) | ||
| return null; | ||
| const current = self.center.add(corners[self.index]); | ||
| self.index += 1; | ||
| return current; | ||
| } | ||
| }; | ||
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| /// Build the hashmap from an iterator of lines | ||
| pub fn parse(allocator: Allocator, input: anytype) !PositionedLetter { | ||
| var result = PositionedLetter.init(allocator); | ||
| var lines = utils.lineIterator(input); | ||
| var y: i32 = 0; | ||
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| while (lines.next()) |line| { | ||
| for (line, 0..line.len) |c, x| { | ||
| try result.put(.{ .x = @intCast(x), .y = y }, c); | ||
| } | ||
| y += 1; | ||
| } | ||
| return result; | ||
| } | ||
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| pub fn part1(input: PositionedLetter) u32 { | ||
| var iter = input.iterator(); | ||
| var result: u32 = 0; | ||
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| while (iter.next()) |letter| { | ||
| if (letter.value_ptr.* == 'X') { | ||
| for (directions) |direction| { | ||
| var ray: RayIterator = .{ .current = letter.key_ptr.*, .move = direction }; | ||
| var i: u32 = 0; | ||
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| while (ray.next()) |p| { | ||
| if (input.get(p) orelse break != "MAS"[i]) | ||
| break; | ||
| i += 1; | ||
| if (i > 2) { | ||
| result += 1; | ||
| break; | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| return result; | ||
| } | ||
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| pub fn part2(input: PositionedLetter) u32 { | ||
| var iter = input.iterator(); | ||
| var result: u32 = 0; | ||
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| outer: while (iter.next()) |letter| { | ||
| if (letter.value_ptr.* == 'A') { | ||
| var corners = letter.key_ptr.corners(); | ||
| var surroundings: [4]u8 = undefined; | ||
| var i: u32 = 0; | ||
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| while (corners.next()) |corner| { | ||
| const c = input.get(corner) orelse continue :outer; | ||
| surroundings[i] = c; | ||
| i += 1; | ||
| } | ||
| if (std.mem.indexOf(u8, "MSSMMSS", &surroundings) != null) { | ||
| result += 1; | ||
| } | ||
| } | ||
| } | ||
| return result; | ||
| } | ||
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| pub fn main() !void { | ||
| var gpa: std.heap.GeneralPurposeAllocator(.{}) = .{}; | ||
| defer _ = gpa.deinit(); | ||
| const allocator = gpa.allocator(); | ||
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| var stdin = std.io.bufferedReader(std.io.getStdIn().reader()); | ||
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| var input = try parse(allocator, stdin.reader()); | ||
| defer input.deinit(); | ||
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| std.debug.print("Number of 'XMAS' : {:5}\n", .{part1(input)}); | ||
| std.debug.print("Number of X 'MAS': {:5}\n", .{part2(input)}); | ||
| } | ||
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| // -------------------- Tests -------------------- | ||
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| test part1 { | ||
| const sample = | ||
| \\MMMSXXMASM | ||
| \\MSAMXMSMSA | ||
| \\AMXSXMAAMM | ||
| \\MSAMASMSMX | ||
| \\XMASAMXAMM | ||
| \\XXAMMXXAMA | ||
| \\SMSMSASXSS | ||
| \\SAXAMASAAA | ||
| \\MAMMMXMMMM | ||
| \\MXMXAXMASX | ||
| ; | ||
| var stream = std.io.fixedBufferStream(sample); | ||
| var input = try parse(std.testing.allocator, stream.reader()); | ||
| defer input.deinit(); | ||
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| try std.testing.expectEqual(18, part1(input)); | ||
| try std.testing.expectEqual(9, part2(input)); | ||
| } |
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