Rider for Unreal Engine at work. Neovim at work/home for literally everything else (web, golang, python, zig). I have vscodium as well, a glorified config file editor basically.

Let’s encrypt brother

Zig

const std = @import("std");
const List = std.ArrayList;
const Map = std.AutoHashMap;

const tokenizeScalar = std.mem.tokenizeScalar;
const splitScalar = std.mem.splitScalar;
const parseInt = std.fmt.parseInt;
const print = std.debug.print;
const contains = std.mem.containsAtLeast;
const eql = std.mem.eql;

var gpa = std.heap.GeneralPurposeAllocator(.{}){};
const alloc = gpa.allocator();

const Answer = struct {
    middle_sum: i32,
    reordered_sum: i32,
};

pub fn solve(input: []const u8) !Answer {
    var rows = splitScalar(u8, input, '\n');

    // key is a page number and value is a
    // list of pages to be printed before it
    var rules = Map(i32, List(i32)).init(alloc);
    var pages = List([]i32).init(alloc);
    defer {
        var iter = rules.iterator();
        while (iter.next()) |rule| {
            rule.value_ptr.deinit();
        }
        rules.deinit();
        pages.deinit();
    }

    var parse_rules = true;
    while (rows.next()) |row| {
        if (eql(u8, row, "")) {
            parse_rules = false;
            continue;
        }

        if (parse_rules) {
            var rule_pair = tokenizeScalar(u8, row, '|');
            const rule = try rules.getOrPut(try parseInt(i32, rule_pair.next().?, 10));
            if (!rule.found_existing) {
                rule.value_ptr.* = List(i32).init(alloc);
            }
            try rule.value_ptr.*.append(try parseInt(i32, rule_pair.next().?, 10));
        } else {
            var page = List(i32).init(alloc);
            var page_list = tokenizeScalar(u8, row, ',');
            while (page_list.next()) |list| {
                try page.append(try parseInt(i32, list, 10));
            }
            try pages.append(try page.toOwnedSlice());
        }
    }

    var middle_sum: i32 = 0;
    var reordered_sum: i32 = 0;

    var wrong_order = false;
    for (pages.items) |page| {
        var index: usize = page.len - 1;
        while (index > 0) : (index -= 1) {
            var page_rule = rules.get(page[index]) orelse continue;

            // check the rest of the pages
            var remaining: usize = 0;
            while (remaining < page[0..index].len) {
                if (contains(i32, page_rule.items, 1, &[_]i32{page[remaining]})) {
                    // re-order the wrong page
                    const element = page[remaining];
                    page[remaining] = page[index];
                    page[index] = element;
                    wrong_order = true;

                    if (rules.get(element)) |next_rule| {
                        page_rule = next_rule;
                    }

                    continue;
                }
                remaining += 1;
            }
        }
        if (wrong_order) {
            reordered_sum += page[(page.len - 1) / 2];
            wrong_order = false;
        } else {
            // middle page number
            middle_sum += page[(page.len - 1) / 2];
        }
    }
    return Answer{ .middle_sum = middle_sum, .reordered_sum = reordered_sum };
}

pub fn main() !void {
    const answer = try solve(@embedFile("input.txt"));
    print("Part 1: {d}\n", .{answer.middle_sum});
    print("Part 2: {d}\n", .{answer.reordered_sum});
}

test "test input" {
    const answer = try solve(@embedFile("test.txt"));
    try std.testing.expectEqual(143, answer.middle_sum);
    try std.testing.expectEqual(123, answer.reordered_sum);
}

Zig

const std = @import("std");
const List = std.ArrayList;

const tokenizeScalar = std.mem.tokenizeScalar;
const parseInt = std.fmt.parseInt;
const print = std.debug.print;
const eql = std.mem.eql;

var gpa = std.heap.GeneralPurposeAllocator(.{}){};
const alloc = gpa.allocator();

const Point = struct {
    x: isize,
    y: isize,
    fn add(self: *const Point, point: *const Point) Point {
        return Point{ .x = self.x + point.x, .y = self.y + point.y };
    }
};

// note: i have no idea how to use this or if it's even possible
// const DirectionType = enum(u8) { Up, Down, Left, Right, UpLeft, UpRight, DownLeft, DownRight };
// const Direction = union(DirectionType) {
//     up: Point = .{ .x = 0, .y = 0 },
// };

const AllDirections = [_]Point{
    .{ .x = 0, .y = -1 }, // up
    .{ .x = 0, .y = 1 }, // down
    .{ .x = -1, .y = 0 }, // left
    .{ .x = 1, .y = 0 }, // right
    .{ .x = -1, .y = -1 }, // up left
    .{ .x = 1, .y = -1 }, // up right
    .{ .x = -1, .y = 1 }, // down left
    .{ .x = 1, .y = 1 }, // down right
};

const Answer = struct {
    xmas: u32,
    mas: u32,
};

pub fn searchXmas(letters: List([]const u8), search_char: u8, position: Point, direction: Point) u32 {
    const current_char = getChar(letters, position);
    if (current_char == search_char) {
        const next = position.add(&direction);
        if (current_char == 'M') {
            return searchXmas(letters, 'A', next, direction);
        } else if (current_char == 'A') {
            return searchXmas(letters, 'S', next, direction);
        } else if (current_char == 'S') {
            return 1; // found all letters
        }
    }
    return 0;
}

pub fn countXmas(letters: List([]const u8), starts: List(Point)) u32 {
    var counter: u32 = 0;
    for (starts.items) |start| {
        for (AllDirections) |direction| {
            const next = start.add(&direction);
            counter += searchXmas(letters, 'M', next, direction);
        }
    }
    return counter;
}

pub fn countMas(letters: List([]const u8), starts: List(Point)) u32 {
    var counter: u32 = 0;
    for (starts.items) |start| {
        const a_char = getChar(letters, start) orelse continue;
        const top_left_char = getChar(letters, start.add(&AllDirections[4])) orelse continue;
        const down_right_char = getChar(letters, start.add(&AllDirections[7])) orelse continue;
        const top_right_char = getChar(letters, start.add(&AllDirections[5])) orelse continue;
        const down_left_char = getChar(letters, start.add(&AllDirections[6])) orelse continue;

        const tldr = [3]u8{ top_left_char, a_char, down_right_char };
        const trdl = [3]u8{ top_right_char, a_char, down_left_char };
        if ((eql(u8, &tldr, "MAS") or eql(u8, &tldr, "SAM")) and (eql(u8, &trdl, "MAS") or eql(u8, &trdl, "SAM"))) {
            counter += 1;
        }
    }
    return counter;
}

pub fn getChar(letters: List([]const u8), point: Point) ?u8 {
    if (0 > point.x or point.x >= letters.items.len) {
        return null;
    }
    const row = @as(usize, @intCast(point.x));

    if (0 > point.y or point.y >= letters.items[row].len) {
        return null;
    }
    const col = @as(usize, @intCast(point.y));
    return letters.items[row][col];
}

pub fn solve(input: []const u8) !Answer {
    var rows = tokenizeScalar(u8, input, '\n');

    var letters = List([]const u8).init(alloc);
    defer letters.deinit();
    var x_starts = List(Point).init(alloc);
    defer x_starts.deinit();
    var a_starts = List(Point).init(alloc);
    defer a_starts.deinit();

    var x: usize = 0;
    while (rows.next()) |row| {
        try letters.append(row);
        for (row, 0..) |letter, y| {
            if (letter == 'X') {
                try x_starts.append(.{ .x = @intCast(x), .y = @intCast(y) });
            } else if (letter == 'A') {
                try a_starts.append(.{ .x = @intCast(x), .y = @intCast(y) });
            }
        }
        x += 1;
    }

    // PART 1
    const xmas = countXmas(letters, x_starts);

    // PART 2
    const mas = countMas(letters, a_starts);

    return Answer{ .xmas = xmas, .mas = mas };
}

pub fn main() !void {
    const answer = try solve(@embedFile("input.txt"));
    print("Part 1: {d}\n", .{answer.xmas});
    print("Part 2: {d}\n", .{answer.mas});
}

test "test input" {
    const answer = try solve(@embedFile("test.txt"));
    try std.testing.expectEqual(18, answer.xmas);
}

#Zig

const std = @import("std");
const List = std.ArrayList;

const splitScalar = std.mem.splitScalar;
const parseInt = std.fmt.parseInt;
const print = std.debug.print;
const concat = std.mem.concat;

var gpa = std.heap.GeneralPurposeAllocator(.{}){};
const alloc = gpa.allocator();

const Answer = struct {
    safe: u32,
    tolerated: u32,
};

pub fn isSafe(levels: []i32) bool {
    if (levels.len == 0) {
        return false;
    }
    // slide window in pairs, advancing by one
    var it = std.mem.window(i32, levels, 2, 1);
    const first = it.first();
    const decreasing = first[0] - first[1] > 0;
    it.reset(); // rewind the iterator

    while (it.next()) |slice| {
        const lhs: i32 = slice[0];
        const rhs: i32 = slice[1];
        if (decreasing) {
            if (lhs <= rhs) return false;
            if (lhs - rhs < 1 or lhs - rhs > 3) return false;
        } else {
            if (rhs <= lhs) return false;
            if (rhs - lhs < 1 or rhs - lhs > 3) return false;
        }
    }
    return true;
}

pub fn solve(input: []const u8) !Answer {
    var rows = splitScalar(u8, input, '\n');

    // PART 1

    // determine how many reports are safe
    var safe_reports: u32 = 0;
    var tolerated_reports: u32 = 0;
    var unsafe_reports = List([]i32).init(alloc);
    defer unsafe_reports.deinit();

    while (rows.next()) |row| {
        var levels = splitScalar(u8, row, ' ');

        var report = List(i32).init(alloc);
        defer report.deinit();

        while (levels.next()) |level| {
            const value = parseInt(i32, level, 10) catch continue;
            report.append(value) catch continue;
        }

        if (isSafe(report.items)) {
            safe_reports += 1;
        } else {
            try unsafe_reports.append(try alloc.dupe(i32, report.items));
        }
    }

    // PART 2

    // determine how many unsafe reports can be tolerated
    for (unsafe_reports.items) |report| {
        var index: usize = 0;
        while (index < report.len) : (index += 1) {
            // mutate report by removing one level
            const mutated_report = concat(
                alloc,
                i32,
                &[_][]const i32{ report[0..index], report[index + 1 ..] },
            ) catch report;
            defer alloc.free(mutated_report);

            if (isSafe(mutated_report)) {
                tolerated_reports += 1;
                break;
            }
        }
    }

    return Answer{ .safe = safe_reports, .tolerated = safe_reports + tolerated_reports };
}

pub fn main() !void {
    const answer = try solve(@embedFile("input.txt"));
    print("Part 1: {d}\n", .{answer.safe});
    print("Part 2: {d}\n", .{answer.tolerated});
}

test "test input" {
    const answer = try solve(@embedFile("test.txt"));
    try std.testing.expectEqual(2, answer.safe);
    try std.testing.expectEqual(4, answer.tolerated);

Zig

const std = @import("std");
const List = std.ArrayList;
const Map = std.AutoHashMap;

const splitSeq = std.mem.splitSequence;
const splitScalar = std.mem.splitScalar;
const parseInt = std.fmt.parseInt;
const print = std.debug.print;
const sort = std.sort.block;

var gpa = std.heap.GeneralPurposeAllocator(.{}){};
const alloc = gpa.allocator();

const Answer = struct {
    distance: u32,
    similarity: u32,
};

fn lessThan(_: void, lhs: []const u8, rhs: []const u8) bool {
    return std.mem.lessThan(u8, lhs, rhs);
}

pub fn solve(input: []const u8) !Answer {
    var rows = splitScalar(u8, input, '\n');
    var left_list = List([]const u8).init(alloc);
    defer left_list.deinit();
    var right_list = List([]const u8).init(alloc);
    defer right_list.deinit();

    // PART 1

    // split the rows into two lists
    while (rows.next()) |row| {
        var sides = splitSeq(u8, row, "   ");
        try left_list.append(sides.next() orelse break);
        try right_list.append(sides.next() orelse break);
    }
    _ = left_list.pop(); // last null

    // sort both lists
    sort([]const u8, left_list.items, {}, lessThan);
    sort([]const u8, right_list.items, {}, lessThan);

    var distance: u32 = 0;
    for (left_list.items, right_list.items) |left, right| {
        distance += @abs(try parseInt(i32, left, 10) - try parseInt(i32, right, 10));
    }

    // PART 2
    var right_scores = Map(i32, u32).init(alloc);
    defer right_scores.deinit();

    // count number of item appearances in the right list
    for (right_list.items) |item| {
        const value = try parseInt(i32, item, 10);
        const result = try right_scores.getOrPut(value);
        if (!result.found_existing) {
            result.value_ptr.* = 1;
        } else {
            result.value_ptr.* += 1;
        }
    }

    // sum up similarity between items in left list and right list scores
    var similarity: u32 = 0;
    for (left_list.items) |item| {
        const value = try parseInt(i32, item, 10);
        const result = right_scores.get(value) orelse 0;
        similarity += @as(u32, @intCast(value)) * result;
    }
    return Answer{ .distance = distance, .similarity = similarity };
}

pub fn main() !void {
    const answer = try solve(@embedFile("input.txt"));
    print("Part 1: {d}\n", .{answer.distance});
    print("Part 2: {d}\n", .{answer.similarity});
}

test "test input" {
    const answer = try solve(@embedFile("test.txt"));
    try std.testing.expectEqual(answer.distance, 11);
    try std.testing.expectEqual(answer.similarity, 31);
}

Been trying to pick up zig, so made sense to try the AoC with it as well.

It’s a reader assistance, some paid for tool that highlights parts of a word, can’t recall what it’s called…