aoc2025/day1/day1a.zig

const std = @import("std");

const allocator = std.heap.page_allocator;

const Dial = struct {
    v: i32 = 50,

    fn Left(self: *Dial, count: u32) void {
        self.v -= @intCast(count % 100);
        if (self.v < 0) {
          self.v += 100;
        } 
    }

    fn Right(self: *Dial, count: u32) void {
        self.v += @intCast(count % 100);
        if (self.v >= 100) {
          self.v -= 100;
        } 
    }
};

pub fn main() !void {
    const inputFile = try std.fs.cwd().openFile(
        "input.txt",
        .{
            .mode = .read_only,
        },
    );
    defer inputFile.close();

    var inputFileBuffer: [1024]u8 = undefined;
    var inputFileReader = inputFile.reader(&inputFileBuffer);
    const inputFileSize = try inputFileReader.getSize();
    var printBuf: [1024]u8 = undefined;

    const inputBuffer = try allocator.alloc(u8, inputFileSize);
    try inputFileReader.interface.readSliceAll(inputBuffer);

    var dial: Dial = .{};
    var zeroCount: i32 = 0;

    var it = std.mem.tokenizeScalar(u8, inputBuffer, '\n');
    while (it.next()) |token| {
        const direction = token[0];
        const count = try std.fmt.parseInt(u32, token[1..], 10);

        if (direction == 'L') {
            dial.Left(count);
        } else {
            dial.Right(count);
        }

        if (dial.v == 0) {
            zeroCount += 1;
        }
    }

    try std.fs.File.stdout().writeAll(try std.fmt.bufPrint(&printBuf, "{d}\n", .{zeroCount}));
}