day2.zig

day2.zig

const std = @import("std");
const Complex = struct { i64, i64 };
fn mul(complex1: Complex, complex2: Complex) Complex {
    // std.debug.print("{any}:{any}\n", .{ complex1, complex2 });
    return .{ (complex1.@"0" * complex2.@"0") - (complex1.@"1" * complex2.@"1"), (complex1.@"0" * complex2.@"1") + (complex1.@"1" * complex2.@"0") };
}

fn add(complex1: Complex, complex2: Complex) Complex {
    return .{ complex1.@"0" + complex2.@"0", complex1.@"1" + complex2.@"1" };
}
fn div(complex1: Complex, complex2: Complex) Complex {
    return .{ @divTrunc(complex1.@"0", complex2.@"0"), @divTrunc(complex1.@"1", complex2.@"1") };
}
fn part1(A: struct { i64, i64 }, _div: Complex, n_counts: usize) ?Complex {
    var R: Complex = .{ 0, 0 };
    for (0..n_counts) |_| {
        R = mul(R, R);
        R = div(R, _div);
        R = add(R, A);
        if (@abs(R.@"0") >= 1000_000 or @abs(R.@"1") >= 1000_000) return null;
    }
    return R;
}
fn part2(A: struct { i64, i64 }, grid_size: usize, grid_len: usize) i64 {
    var counter: i32 = 0;
    const ppsize = std.math.cast(i64, grid_len / (grid_size - 1)).?;
    for (0..grid_size) |_row| {
        for (0..grid_size) |_col| {
            const row = std.math.cast(i64, _row).?;
            const col = std.math.cast(i64, _col).?;
            const point: Complex = .{ A.@"0" + row * ppsize, A.@"1" + col * ppsize };
            const result = part1(point, .{ 100000, 100000 }, 100);
            if (result == null) continue;
            counter += 1;
        }
    }
    return counter;
}

pub fn main() !void {
    const R = part1(part1_input, .{ 10, 10 }, 3);
    std.debug.print("{any}\n", .{R.?});

    // part2 solution
    var n_points = part2(part2_input, 101, 1000);
    std.debug.print("{d}\n", .{n_points});

    // part3 solution
    n_points = part2(part3_input, 1001, 1000);
    std.debug.print("{d}\n", .{n_points});
}