diff --git a/day21-easy/build.zig b/day21-easy/build.zig new file mode 100644 index 0000000..eceeebd --- /dev/null +++ b/day21-easy/build.zig @@ -0,0 +1,70 @@ +const std = @import("std"); + +// Although this function looks imperative, note that its job is to +// declaratively construct a build graph that will be executed by an external +// runner. +pub fn build(b: *std.Build) void { + // Standard target options allows the person running `zig build` to choose + // what target to build for. Here we do not override the defaults, which + // means any target is allowed, and the default is native. Other options + // for restricting supported target set are available. + const target = b.standardTargetOptions(.{}); + + // Standard optimization options allow the person running `zig build` to select + // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall. Here we do not + // set a preferred release mode, allowing the user to decide how to optimize. + const optimize = b.standardOptimizeOption(.{}); + + const exe = b.addExecutable(.{ + .name = "day21-easy", + // In this case the main source file is merely a path, however, in more + // complicated build scripts, this could be a generated file. + .root_source_file = .{ .path = "src/main.zig" }, + .target = target, + .optimize = optimize, + }); + + // This declares intent for the executable to be installed into the + // standard location when the user invokes the "install" step (the default + // step when running `zig build`). + b.installArtifact(exe); + + // This *creates* a Run step in the build graph, to be executed when another + // step is evaluated that depends on it. The next line below will establish + // such a dependency. + const run_cmd = b.addRunArtifact(exe); + + // By making the run step depend on the install step, it will be run from the + // installation directory rather than directly from within the cache directory. + // This is not necessary, however, if the application depends on other installed + // files, this ensures they will be present and in the expected location. + run_cmd.step.dependOn(b.getInstallStep()); + + // This allows the user to pass arguments to the application in the build + // command itself, like this: `zig build run -- arg1 arg2 etc` + if (b.args) |args| { + run_cmd.addArgs(args); + } + + // This creates a build step. It will be visible in the `zig build --help` menu, + // and can be selected like this: `zig build run` + // This will evaluate the `run` step rather than the default, which is "install". + const run_step = b.step("run", "Run the app"); + run_step.dependOn(&run_cmd.step); + + // Creates a step for unit testing. This only builds the test executable + // but does not run it. + const unit_tests = b.addTest(.{ + .root_source_file = .{ .path = "src/main.zig" }, + .target = target, + .optimize = optimize, + }); + + const run_unit_tests = b.addRunArtifact(unit_tests); + + // Similar to creating the run step earlier, this exposes a `test` step to + // the `zig build --help` menu, providing a way for the user to request + // running the unit tests. + const test_step = b.step("test", "Run unit tests"); + test_step.dependOn(&run_unit_tests.step); +} diff --git a/day21-easy/easy.in b/day21-easy/easy.in new file mode 100644 index 0000000..a0a9a91 --- /dev/null +++ b/day21-easy/easy.in @@ -0,0 +1,131 @@ +................................................................................................................................... +..............#...#........#...............#.#.......#....##...........#.#..#......#.....#.........#..##........................... 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+....#.#.##..#..#....................#.................#.##.............#....#....#.............###...#...#..##....#.....##......... +.............#.......#...............#........#.#.....#..#.#................#.....#..##.....#....#...............#....#......#...#. +................................................................................................................................... \ No newline at end of file diff --git a/day21-easy/sample.in b/day21-easy/sample.in new file mode 100644 index 0000000..c66328c --- /dev/null +++ b/day21-easy/sample.in @@ -0,0 +1,11 @@ +........... +.....###.#. +.###.##..#. +..#.#...#.. +....#.#.... +.##..S####. +.##..#...#. +.......##.. +.##.#.####. +.##..##.##. +........... \ No newline at end of file diff --git a/day21-easy/src/main.zig b/day21-easy/src/main.zig new file mode 100644 index 0000000..2f0b2bd --- /dev/null +++ b/day21-easy/src/main.zig @@ -0,0 +1,102 @@ +const std = @import("std"); + +const CellStatus = enum(u2) { + Rock = 0, + Reachable = 1, + ReachedEven = 2, + ReachedOdd = 3, +}; + +const Map = [256][256]CellStatus; + +fn solveMap(map: Map) usize { + const height = map.len; + const width = map[0].len; + var current_map = map; + for (0..64) |i| { + _ = i; + var next_map = current_map; + for (0..height) |row| { + for (0..width) |column| { + const maybe_next_status: ?CellStatus = switch (current_map[row][column]) { + .ReachedEven => .ReachedOdd, + .ReachedOdd => .ReachedEven, + else => null, + }; + + if (maybe_next_status) |next_status| { + if (row > 0 and next_map[row - 1][column] == .Reachable) { + next_map[row - 1][column] = next_status; + } + + if (row + 1 < height and next_map[row + 1][column] == .Reachable) { + next_map[row + 1][column] = next_status; + } + + if (column > 0 and next_map[row][column - 1] == .Reachable) { + next_map[row][column - 1] = next_status; + } + + if (column + 1 < width and next_map[row][column + 1] == .Reachable) { + next_map[row][column + 1] = next_status; + } + } + } + } + + current_map = next_map; + } + + var result: usize = 0; + for (0..height) |row| { + for (0..width) |column| { + if (current_map[row][column] == .ReachedEven) { + result += 1; + } + } + } + + return result; +} + +pub fn solveAll(reader: anytype) !usize { + var result: usize = 0; + while (true) { + var map = std.mem.zeroes(Map); + + var row: usize = 0; + var empty_line_reached = false; + var line_buffer: [1000]u8 = undefined; + while (try reader.readUntilDelimiterOrEof(&line_buffer, '\n')) |line| { + if (line.len == 0) { + empty_line_reached = true; + break; + } + for (line, 0..) |char, column| { + map[row][column] = switch (char) { + '#' => .Rock, + '.' => .Reachable, + 'S' => .ReachedEven, + else => unreachable, + }; + } + row += 1; + } + + result += solveMap(map); + + if (!empty_line_reached) { + return result; + } + } +} + +pub fn main() !void { + const stdout = std.io.getStdOut().writer(); + + const raw_in = std.io.getStdIn(); + var buffered_reader = std.io.bufferedReader(raw_in.reader()); + var reader = buffered_reader.reader(); + const result = try solveAll(&reader); + try stdout.print("{d}\n", .{result}); +}