aoc-2020-zig

Advent of Code 2020 Solutions in Zig
git clone https://git.sinitax.com/sinitax/aoc-2020-zig
Log | Files | Refs | README | sfeed.txt

main.zig (2698B)

      1const std = @import("std");
      2const aoc = @import("aoc");
      3const Pos = aoc.Pos;
      4const Dir = aoc.Dir;
      5
      6const Ship = struct { pos: Pos, waypoint: Pos, dir: usize };
      7
      8fn part1(allocator: std.mem.Allocator, input: []u8, args: [][]u8) !?[]u8 {
      9    _ = args;
     10
     11    var ship = Ship{ .pos = Pos{ .x = 0, .y = 0 }, .waypoint = Pos{ .x = 0, .y = 0 }, .dir = 0 };
     12    var lineit = std.mem.tokenize(u8, input, "\n");
     13    while (lineit.next()) |line| {
     14        const val = try std.fmt.parseInt(u32, line[1..], 10);
     15        switch (line[0]) {
     16            'N' => ship.pos = ship.pos.add(Dir.North.mult(val)),
     17            'S' => ship.pos = ship.pos.add(Dir.South.mult(val)),
     18            'E' => ship.pos = ship.pos.add(Dir.East.mult(val)),
     19            'W' => ship.pos = ship.pos.add(Dir.West.mult(val)),
     20            'L' => ship.dir = Dir.nextCCW(ship.dir, @divExact(val, 90)),
     21            'R' => ship.dir = Dir.nextCW(ship.dir, @divExact(val, 90)),
     22            'F' => ship.pos = ship.pos.add(Dir.dirs[ship.dir].mult(val)),
     23            else => {
     24                return aoc.Error.InvalidInput;
     25            },
     26        }
     27    }
     28
     29    const answer = std.math.absCast(ship.pos.x) + std.math.absCast(ship.pos.y);
     30
     31    return try std.fmt.allocPrint(allocator, "{d}", .{answer});
     32}
     33
     34fn part2(allocator: std.mem.Allocator, input: []u8, args: [][]u8) !?[]u8 {
     35    _ = args;
     36
     37    var ship = Ship{ .pos = Pos{ .x = 0, .y = 0 }, .waypoint = Pos{ .x = 10, .y = 1 }, .dir = 0 };
     38    var lineit = std.mem.tokenize(u8, input, "\n");
     39    while (lineit.next()) |line| {
     40        const val = try std.fmt.parseInt(u32, line[1..], 10);
     41        switch (line[0]) {
     42            'N' => ship.waypoint = ship.waypoint.add(Dir.North.mult(val)),
     43            'S' => ship.waypoint = ship.waypoint.add(Dir.South.mult(val)),
     44            'E' => ship.waypoint = ship.waypoint.add(Dir.East.mult(val)),
     45            'W' => ship.waypoint = ship.waypoint.add(Dir.West.mult(val)),
     46            'L' => {
     47                var new = Dir.rotCCW(ship.waypoint, @divExact(val, 90));
     48                ship.waypoint = new;
     49            },
     50            'R' => {
     51                var new = Dir.rotCW(ship.waypoint, @divExact(val, 90));
     52                ship.waypoint = new;
     53            },
     54            'F' => ship.pos = ship.pos.add(ship.waypoint.mult(val)),
     55            else => {
     56                return aoc.Error.InvalidInput;
     57            },
     58        }
     59        aoc.debugfmt("{s} {} {} {} {}\n", .{ line, ship.waypoint.x, ship.waypoint.y, ship.pos.x, ship.pos.y });
     60    }
     61
     62    const answer = std.math.absCast(ship.pos.x) + std.math.absCast(ship.pos.y);
     63
     64    return try std.fmt.allocPrint(allocator, "{d}", .{answer});
     65}
     66
     67pub const main = aoc.main(part1, part2, .{ "1191", "61053" });