day 1, part 2

day01-hard/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 = "day01-hard",
+        // 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);
+}

day01-hard/sample.in

@@ -0,0 +1,4 @@
+1abc2
+pqr3stu8vwx
+a1b2c3d4e5f
+treb7uchet

day01-hard/sample2.in

@@ -0,0 +1,7 @@
+two1nine
+eightwothree
+abcone2threexyz
+xtwone3four
+4nineeightseven2
+zoneight234
+7pqrstsixteen

day01-hard/src/main.zig

@@ -0,0 +1,236 @@
+const std = @import("std");
+
+// Cannot believe I'm doing this by hand,
+// but both somewhat popular regex libraries for Zig
+// have build scripts incompatible with latest Zig 0.11 (released on August 4th, 2023),
+// and I'm not into trying to link this with regex.h
+
+fn get_digit_at_start(substr: []const u8) ?u8 {
+    return switch (substr[0]) {
+        '0'...'9' => substr[0] - '0',
+        'o' => if (substr.len >= 3 and substr[1] == 'n' and substr[2] == 'e') 1 else null,
+        't' => if (substr.len >= 3)
+            switch (substr[1]) {
+                'w' => if (substr[2] == 'o') 2 else null,
+                'h' => if (substr.len >= 5 and substr[2] == 'r' and substr[3] == 'e' and substr[4] == 'e') 3 else null,
+                else => null,
+            }
+        else
+            null,
+        'f' => if (substr.len >= 4)
+            switch (substr[1]) {
+                'o' => if (substr[2] == 'u' and substr[3] == 'r') 4 else null,
+                'i' => if (substr[2] == 'v' and substr[3] == 'e') 5 else null,
+                else => null,
+            }
+        else
+            null,
+        's' => if (substr.len >= 3)
+            switch (substr[1]) {
+                'i' => if (substr[2] == 'x') 6 else null,
+                'e' => if (substr.len >= 5 and substr[2] == 'v' and substr[3] == 'e' and substr[4] == 'n') 7 else null,
+                else => null,
+            }
+        else
+            null,
+        'e' => if (substr.len >= 5 and substr[1] == 'i' and substr[2] == 'g' and substr[3] == 'h' and substr[4] == 't') 8 else null,
+        'n' => if (substr.len >= 4 and substr[1] == 'i' and substr[2] == 'n' and substr[3] == 'e') 9 else null,
+        else => null,
+    };
+}
+
+fn get_digit_at_end(substr: []const u8) ?u8 {
+    const last = substr.len - 1;
+    return switch (substr[last]) {
+        '0'...'9' => substr[last] - '0',
+        'e' => if (substr.len >= 3)
+            switch (substr[last - 1]) {
+                'n' => switch (substr[last - 2]) {
+                    'o' => 1,
+                    'i' => if (substr.len >= 4 and substr[last - 3] == 'n') 9 else null,
+                    else => null,
+                },
+                'e' => if (substr.len >= 5 and substr[last - 2] == 'r' and substr[last - 3] == 'h' and substr[last - 4] == 't') 3 else null,
+                'v' => if (substr.len >= 4 and substr[last - 2] == 'i' and substr[last - 3] == 'f') 5 else null,
+                else => null,
+            }
+        else
+            null,
+        'o' => if (substr.len >= 3 and substr[last - 1] == 'w' and substr[last - 2] == 't') 2 else null,
+        'r' => if (substr.len >= 4 and substr[last - 1] == 'u' and substr[last - 2] == 'o' and substr[last - 3] == 'f') 4 else null,
+        'x' => if (substr.len >= 3 and substr[last - 1] == 'i' and substr[last - 2] == 's') 6 else null,
+        'n' => if (substr.len >= 5 and substr[last - 1] == 'e' and substr[last - 2] == 'v' and substr[last - 3] == 'e' and substr[last - 4] == 's') 7 else null,
+        't' => if (substr.len >= 5 and substr[last - 1] == 'h' and substr[last - 2] == 'g' and substr[last - 3] == 'i' and substr[last - 4] == 'e') 8 else null,
+        else => null,
+    };
+}
+
+fn get_first_digit(str: []const u8) u8 {
+    for (0..str.len) |i| {
+        const digit = get_digit_at_start(str[i..]);
+        if (digit != null) {
+            return digit.?;
+        }
+    }
+
+    return 0;
+}
+
+fn get_last_digit(str: []const u8) u8 {
+    for (0..str.len) |i| {
+        const digit = get_digit_at_end(str[0 .. str.len - i]);
+        if (digit != null) {
+            return digit.?;
+        }
+    }
+
+    return 0;
+}
+
+fn get_value(str: []const u8) u8 {
+    const first_digit = get_first_digit(str);
+    const last_digit = get_last_digit(str);
+    return first_digit * 10 + last_digit;
+}
+
+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 result: u32 = 0;
+    var line_buffer: [1000]u8 = undefined;
+    while (try reader.readUntilDelimiterOrEof(&line_buffer, '\n')) |line| {
+        result += get_value(line);
+    }
+    try stdout.print(
+        "{d}\n",
+        .{result},
+    );
+}
+
+test "get digit at start" {
+    try std.testing.expectEqual(@as(?u8, 1), get_digit_at_start("one"));
+    try std.testing.expectEqual(@as(?u8, 1), get_digit_at_start("one!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("on"));
+
+    try std.testing.expectEqual(@as(?u8, 2), get_digit_at_start("two"));
+    try std.testing.expectEqual(@as(?u8, 2), get_digit_at_start("two!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("tw"));
+
+    try std.testing.expectEqual(@as(?u8, 3), get_digit_at_start("three"));
+    try std.testing.expectEqual(@as(?u8, 3), get_digit_at_start("three!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("thre"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("thre!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("thr!e"));
+
+    try std.testing.expectEqual(@as(?u8, 4), get_digit_at_start("four"));
+    try std.testing.expectEqual(@as(?u8, 4), get_digit_at_start("four!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("fou"));
+
+    try std.testing.expectEqual(@as(?u8, 5), get_digit_at_start("five"));
+    try std.testing.expectEqual(@as(?u8, 5), get_digit_at_start("five!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("fiv"));
+
+    try std.testing.expectEqual(@as(?u8, 6), get_digit_at_start("six"));
+    try std.testing.expectEqual(@as(?u8, 6), get_digit_at_start("six!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("si"));
+
+    try std.testing.expectEqual(@as(?u8, 7), get_digit_at_start("seven"));
+    try std.testing.expectEqual(@as(?u8, 7), get_digit_at_start("seven!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("seve"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("s!ven"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("sev!n"));
+
+    try std.testing.expectEqual(@as(?u8, 8), get_digit_at_start("eight"));
+    try std.testing.expectEqual(@as(?u8, 8), get_digit_at_start("eight!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("eigh"));
+
+    try std.testing.expectEqual(@as(?u8, 9), get_digit_at_start("nine"));
+    try std.testing.expectEqual(@as(?u8, 9), get_digit_at_start("nine!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("nin"));
+
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("!!!!!!!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("t!!!!!!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("f!!!!!!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("s!!!!!!"));
+
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("t"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("f"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_start("s"));
+}
+
+test "get digit at end" {
+    try std.testing.expectEqual(@as(?u8, 1), get_digit_at_end("one"));
+    try std.testing.expectEqual(@as(?u8, 1), get_digit_at_end("!one"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("ne"));
+
+    try std.testing.expectEqual(@as(?u8, 2), get_digit_at_end("two"));
+    try std.testing.expectEqual(@as(?u8, 2), get_digit_at_end("!two"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("wo"));
+
+    try std.testing.expectEqual(@as(?u8, 3), get_digit_at_end("three"));
+    try std.testing.expectEqual(@as(?u8, 3), get_digit_at_end("!three"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("hree"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("thre!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("thr!e"));
+
+    try std.testing.expectEqual(@as(?u8, 4), get_digit_at_end("four"));
+    try std.testing.expectEqual(@as(?u8, 4), get_digit_at_end("!four"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("our"));
+
+    try std.testing.expectEqual(@as(?u8, 5), get_digit_at_end("five"));
+    try std.testing.expectEqual(@as(?u8, 5), get_digit_at_end("!five"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("ive"));
+
+    try std.testing.expectEqual(@as(?u8, 6), get_digit_at_end("six"));
+    try std.testing.expectEqual(@as(?u8, 6), get_digit_at_end("!six"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("ix"));
+
+    try std.testing.expectEqual(@as(?u8, 7), get_digit_at_end("seven"));
+    try std.testing.expectEqual(@as(?u8, 7), get_digit_at_end("!seven"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("even"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("s!ven"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("sev!n"));
+
+    try std.testing.expectEqual(@as(?u8, 8), get_digit_at_end("eight"));
+    try std.testing.expectEqual(@as(?u8, 8), get_digit_at_end("!eight"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("ight"));
+
+    try std.testing.expectEqual(@as(?u8, 9), get_digit_at_end("nine"));
+    try std.testing.expectEqual(@as(?u8, 9), get_digit_at_end("!nine"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("ine"));
+
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("!!!!!!!"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("!!!!!!e"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("!!!!!ne"));
+
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("e"));
+    try std.testing.expectEqual(@as(?u8, null), get_digit_at_end("ne"));
+}
+
+test "get first digit" {
+    try std.testing.expectEqual(@as(?u8, 1), get_first_digit("1"));
+    try std.testing.expectEqual(@as(?u8, 1), get_first_digit("!1"));
+    try std.testing.expectEqual(@as(?u8, 1), get_first_digit("one"));
+    try std.testing.expectEqual(@as(?u8, 1), get_first_digit("onetwo"));
+    try std.testing.expectEqual(@as(?u8, 1), get_first_digit("oone"));
+    try std.testing.expectEqual(@as(?u8, 1), get_first_digit("onone"));
+    try std.testing.expectEqual(@as(?u8, 5), get_first_digit("fiveight"));
+    try std.testing.expectEqual(@as(?u8, 8), get_first_digit("seveight"));
+    try std.testing.expectEqual(@as(?u8, 0), get_first_digit("seveigh!"));
+}
+
+test "get last digit" {
+    try std.testing.expectEqual(@as(?u8, 1), get_last_digit("1"));
+    try std.testing.expectEqual(@as(?u8, 1), get_last_digit("1!"));
+    try std.testing.expectEqual(@as(?u8, 1), get_last_digit("one"));
+    try std.testing.expectEqual(@as(?u8, 1), get_last_digit("twoone"));
+    try std.testing.expectEqual(@as(?u8, 1), get_last_digit("onee"));
+    try std.testing.expectEqual(@as(?u8, 1), get_last_digit("onene"));
+    try std.testing.expectEqual(@as(?u8, 8), get_last_digit("fiveight"));
+    try std.testing.expectEqual(@as(?u8, 7), get_last_digit("sevene"));
+    try std.testing.expectEqual(@as(?u8, 0), get_last_digit("!evene"));
+}