2024 Advent of Code Day 6 in Zig

2024_Advent_of_Code_Day_6.zig

const std = @import("std");

const map = [_][]const u8{ "..................#................................................................#........#.....................................", "...#...........#...................................................#........................................#.................#...", "...................................#................#.#...............#.................................................#.........", ".....#......#................#.....................................................................#..........#........#......#...", "............................................................................................#.....................#...............", ".....................#..##...#........................#.................#.......................#..#.........#.......#...#......#.", "............##....................................##..................#...............................#....#......................", ".............#............#.#..#.......#...........#..............#...............#.....#.........................................", "....................#..........##.........#.........#................#............................................................", "....#.......#................................................................#...#.#..........................................#.#.", "..#..............#.....................................#..........#.#....#..............#..................#.#............#.......", ".#.......#.........................#........................#..#.....#............................................................", "........#...#......................#...........#......................................#....................#......................", ".............................#..............#........##....#....................#......#....................#............#......#.", "..............#..............#............#.......................##....#..........................................#.........#....", ".............#............#..........#..........#...#.....................................................#.......................", "..#........#.....#..........................................#................................................#...#.#...#..........", "........#.....................#...#..#......#.........................................................#.....##.........#..........", "..............................................................................................#...#...............................", "..#.......................#..........................#......#...................................................................#.", ".......#.........................#..............#.........#.............#.......................................#...#.............", "..................#.................#.......................#....................#....................................#...........", "...#...#.......#......##.#...............#....#..............#..........................................#....#..#.................", "#................................#.......#.....#.......#.............#..................#........#................................", "...........#..................................#.......................................................................#.#..#......", ".......#........#.........................................#..........................#...........................#.....#..........", "................#..#.....................#..#...........................#...........................................#.............", "#...#.......................#................................................#................#................................#..", "..........#...........................#.......#............................................................................#.....#", "..................................#............................................................#..................................", "......................#........#.............#....#.....#.......#..........................#..........................#...........", "...........................##.................#.............#........................#...#..................#.....................", ".............................................................................................................#....#..........#....", "................#...................................#...........#..........#....................#............................#....", "........#....#................................................#................##..#..................................#...........", "...........#....................................................#...#.#......#....................................................", ".......................#.........................................................^....................................#...........", "..........................#.............##..#........#.#....#.......#....................#...........#.........#.....#............", "........#...........................#..#..........................................................#...............................", "....#....................................#....#.........................................#.........#...............................", "...............#...................................#.....#.................................#....................................#.", "......#...............................................................#.............................#........................#....", ".........................#.....#.........................#.#...............#.........#.....#..................#..#.........#......", ".........................................................#......#........##.......................#...#......#................#...", ".......................................#.....#.................................#..................................................", "..................#..................................#..........................................................................#.", "...................#....#.........#.......#................#....................#.........................#......#.....#..#.......", "................................#..............................................................................#....#.............", ".....................#.#.............#.................#..........#.......#.........................................#.............", "......#....................#....................................................................#...#.............................", "........#........#...........#.##.............#........................#............#..............#.........#....#........#......", "........................#.................................................................#.......................................", "............................................................#.....#....................#............#.....#....#............#.....", "...........#............#....#........................................................##............#..............#..............", "...........#...........#.....#..............#..............##....#........#......#................................................", "..#................................................................................#......................#......#................", "....................#.........#......................#.............................#.......#.......................#.............#", "..#...#....#......................................................................................................#...............", "...........#................................................................................#...............................#.....", "....................................#............#..........#.........................#..................................#.......#", "...................#......#...................#............#......#........#................#.............#...........#.........#.", "........................#..................................#........#..................#..........................................", "............#..#...........#..................##....................#...........................................#.................", ".......................................................................................#.....#............#.......................", "...............................................#....#................................#..#..........................#..#...........", "..............#..#.....#.........#....................#.......#..#..............#...............................#.....#...........", "..........#............................#..........................................................................................", "........................................#........#........................................................#.#.....................", "#................#......................#..................................................................................#......", "...............................................................................#................................#.................", "...................................................................................................................#.#........#...", "#........................................................................#......................................#.#...............", "...#......#............#...................#.............#........#..........................................#......#.............", "..............##....#...................................................#......................#..................................", "...............#........................................................................#...........#...#.#.......................", "..........#.#.....#................................#...........#........#.......#.................................................", "#....................#......................................................................................#.....................", "..............#...##...........................................#.............#.......#..................#..............#..........", ".#.............................................#..............................................................................#...", "...#................................#............................................#............................#...................", "..............................#......................................................#..........................................#.", "...................#.....................................#..................................#......#..............................", "....#.#..........##.............#.......#........................##..........#.................#..................................", "#..#................#........##....................................................................................#..............", "........#...#.........................................................................#...........................................", "......................................................#....#...................#..#.................................#.............", "........#...............#........#..............................................#............................#....................", "...#..............................#.........................................##.......................................#....#.......", "...#................#..............#.......#......................................................................................", "........#..................#.............................................................#...........................#....#.......", "......................#.#..........#.......#..................................#..#...#............#...............#...............", ".....#..................#....#..#......#.......................#.....................................................#............", ".....#................................#.........................#..................#.#..........#...#............#.....#..........", "....#...................#....#.#.........#........#..................................................................#....#..#....", "........#...............#......................................#........#..............................#..........................", "....#...#.#.....#..............#..................#..........#...#..#......................#...#..........#......................#", "...........#...................................................................................................#................#.", ".................................##..............#.............................#...............................#..................", "...........#.................#.............##...................................#.......................#.................##......", ".....#..................#......#........#.................................................#..#........................#..#........", "......#.......#......................................................................#.#.........#....#...........................", "..................#.#........................#......#................................................................#......#.....", ".....................#............#...................#.....#....................................#.......#..........#.......#.....", "#.............................#...............................#...#...............................................................", "..##.........#........#......................................#.....................#...#.............#............#..#............", "..........#.....................#..#....................#...#....................#....................#.....................#.....", "...........#..........#...............#..#..........#..............................................#.#............................", "............#...#...#.............#.........#.............................#...............#.......................................", ".........#...........#...............................................................#............................................", ".#..#.................................................................#............#.#.......................##...................", "........##............#...................#................................#......................................................", "............................................#..........................#..........................................................", "#...................#...........#..............#...#............#.#........#.................#......#.............................", "........#....................................#....................................................................................", "...........#.........#..#...............#...........#.....##.#......#....##............#....#....#.#.........##.........#.........", "..#......................#..........#.................#.................#......#.............................#........#...........", "....................#.................#....#..............................#....#.............#....#....#.....................#....", "............#.................#.................................#...............................#..#...........................#..", "...................................................#.....#..............#.......#....................#.#..........................", "..#.........##..#........#...................................................................................#............#.......", ".....#..............................#......................................................................#........#.............", "................................#........##.......#...............#..............#.......#...#.#........#.........................", "..............................#.....................#.........................................#..................................#", "...........#...................##.................#.................................#...............................#........#....", "..............................#...##......#..................#...#................................#......#.......#...............#", ".....................##......#......#.#.......#..............#......#.................#.........#...................#.............", "..........................#................................#...........#..........................................................", "...#.....#....................#.....................#...#.....#.............................#.#....#.....#.#.................#....", "............................#...#........#......................................................................#.....#...........", "............#..........##..................#.............................................................#.....#..#..............." };
const point = struct { i: usize, j: usize };

fn checkMapForTurns() !void {
    var guard: point = .{ .i = 0, .j = 0 };
    var path: [map.len][map[0].len]u8 = undefined;
    var direction: u8 = 'N';
    var visits: u32 = 0;

    for (0..map.len) |i| {
        for (0..map[0].len) |j| {
            if (map[i][j] == '^') {
                guard.i = i;
                guard.j = j;
                path[i][j] = ',';
            }
        }
    }

    while (guard.i < map.len and guard.j < map.len and guard.i > 0 and guard.j > 0) {
        switch (direction) {
            'N' => {
                if (map[guard.i - 1][guard.j] == '#') {
                    direction = 'E';
                } else {
                    guard.i -= 1;
                }
            },
            'E' => {
                if (map[guard.i][guard.j + 1] == '#') {
                    direction = 'S';
                } else {
                    guard.j += 1;
                }
            },
            'S' => {
                if (map[guard.i + 1][guard.j] == '#') {
                    direction = 'W';
                } else {
                    guard.i += 1;
                }
            },
            'W' => {
                if (map[guard.i][guard.j - 1] == '#') {
                    direction = 'N';
                } else {
                    guard.j -= 1;
                }
            },
            else => {},
        }
        path[guard.i][guard.j] = ',';
    }

    for (0..path.len) |i| {
        for (0..path[0].len) |j| {
            if (path[i][j] == ',') {
                visits += 1;
            }
        }
    }

    std.debug.print("Total visits for map: {d}\n", .{visits});
}

fn checkMapForObstacles() !void {
    var obstacles: u32 = 0;

    for (0..map.len) |p| {
        for (0..map[0].len) |q| {
            if (map[p][q] == '.') {
                var guard: point = .{ .i = 0, .j = 0 };
                var path: [map.len][map[0].len]u8 = undefined;
                var direction: u8 = 'N';
                var steps: u32 = 0;

                path[p][q] = 'O';

                for (0..map.len) |i| {
                    for (0..map[0].len) |j| {
                        if (map[i][j] == '^') {
                            guard.i = i;
                            guard.j = j;
                            path[i][j] = direction;
                        }
                    }
                }

                while (guard.i < map.len - 1 and guard.j < map.len - 1 and guard.i > 0 and guard.j > 0) {
                    switch (direction) {
                        'N' => {
                            if (map[guard.i - 1][guard.j] == '#' or path[guard.i - 1][guard.j] == 'O') {
                                direction = 'E';
                            } else {
                                guard.i -= 1;
                            }
                        },
                        'E' => {
                            if (map[guard.i][guard.j + 1] == '#' or path[guard.i][guard.j + 1] == 'O') {
                                direction = 'S';
                            } else {
                                guard.j += 1;
                            }
                        },
                        'S' => {
                            if (map[guard.i + 1][guard.j] == '#' or path[guard.i + 1][guard.j] == 'O') {
                                direction = 'W';
                            } else {
                                guard.i += 1;
                            }
                        },
                        'W' => {
                            if (map[guard.i][guard.j - 1] == '#' or path[guard.i][guard.j - 1] == 'O') {
                                direction = 'N';
                            } else {
                                guard.j -= 1;
                            }
                        },
                        else => {},
                    }

                    if (path[guard.i][guard.j] == direction or steps > map.len * map[0].len) {
                        obstacles += 1;
                        break;
                    } else {
                        steps += 1;
                        path[guard.i][guard.j] = direction;
                    }
                }
            }
        }
    }

    std.debug.print("Total looping obstacles for map: {d}\n", .{obstacles});
}

pub fn main() !void {
    _ = try checkMapForTurns();
    _ = try checkMapForObstacles();
}