From c43fa9ef0c683563eacef73f70f77709bde0d7c6 Mon Sep 17 00:00:00 2001 From: Inga Date: Wed, 6 Dec 2023 17:14:22 +0000 Subject: [PATCH] day 6, part 1 --- day06-easy/build.zig | 70 +++++++++++++++++++++++++++ day06-easy/sample.in | 2 + day06-easy/src/main.zig | 104 ++++++++++++++++++++++++++++++++++++++++ 3 files changed, 176 insertions(+) create mode 100644 day06-easy/build.zig create mode 100644 day06-easy/sample.in create mode 100644 day06-easy/src/main.zig diff --git a/day06-easy/build.zig b/day06-easy/build.zig new file mode 100644 index 0000000..0624da0 --- /dev/null +++ b/day06-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 = "day06-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/day06-easy/sample.in b/day06-easy/sample.in new file mode 100644 index 0000000..b39f49d --- /dev/null +++ b/day06-easy/sample.in @@ -0,0 +1,2 @@ +Time: 7 15 30 +Distance: 9 40 200 \ No newline at end of file diff --git a/day06-easy/src/main.zig b/day06-easy/src/main.zig new file mode 100644 index 0000000..56415f6 --- /dev/null +++ b/day06-easy/src/main.zig @@ -0,0 +1,104 @@ +const std = @import("std"); + +fn StackList(comptime T: type, comptime capacity_type: type, comptime capacity: capacity_type) type { + return struct { + const Self = @This(); + mem: [capacity]T, + length: capacity_type, + + fn add(self: *Self, value: T) void { + self.mem[self.length] = value; + self.length += 1; + } + + fn has(self: *const Self, needle: T) bool { + for (0..self.length) |i| { + if (self.mem[i] == needle) { + return true; + } + } + + return false; + } + + fn getMutableSlice(self: *Self) []T { + return (&self.mem)[0..self.length]; + } + + fn getSlice(self: *const Self) []const T { + return self.mem[0..self.length]; + } + + fn reset(self: *Self) void { + self.length = 0; + } + + fn init() Self { + return Self{ + .mem = undefined, + .length = 0, + }; + } + }; +} + +fn addDigit(result: anytype, digit: u8) void { + result.* = (result.* * 10) + (digit - '0'); +} + +const ParsedLine = StackList(u32, u32, 15); + +fn parseLine(line: []const u8) ParsedLine { + var result = ParsedLine.init(); + + var index: usize = 9; + while (index < line.len) { + while (line[index] == ' ') : (index += 1) {} + + var current_number: u32 = 0; + while (index < line.len and line[index] != ' ') : (index += 1) { + addDigit(¤t_number, line[index]); + } + + result.add(current_number); + } + + return result; +} + +fn solve(times: ParsedLine, distances: ParsedLine) u128 { + var result: u64 = 1; + + for (times.getSlice(), distances.getSlice()) |time, distance| { + // This can be implemented in O(1) by solving the quadratic equation, + // but I'm not in the mood to deal with all the float <-> integer nonsense + // and with all the edge cases. + // Times in AOC inputs are low enough, + // there is not that much of a difference between O(1) and O(time) + + var ways: u32 = 0; + for (0..(time + 1)) |i| { + if (i * (time - i) > distance) { + ways += 1; + } + } + + result *= ways; + } + + 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(); + + var line_buffer: [1000]u8 = undefined; + var times = parseLine((try reader.readUntilDelimiterOrEof(&line_buffer, '\n')).?); + var distances = parseLine((try reader.readUntilDelimiterOrEof(&line_buffer, '\n')).?); + + try stdout.print("{d}\n", .{solve(times, distances)}); +}