Advent of Code 2018 Day 4

aoc2018_4.cs

	class Day4_2018 {
		const string INPUTFILE = @"2018\day4.txt";

		public void Part1() {
			var guardSleepMinutes = LoadGuardSleepMinutes();

			var guardSleepTotals = new Dictionary<int, int>();

			foreach (var guard in guardSleepMinutes) {
				if (!guardSleepTotals.ContainsKey(guard.Key)) {
					guardSleepTotals.Add(guard.Key, 0);
				}

				foreach (var minute in guard.Value) {
					guardSleepTotals[guard.Key] += minute;
				}
			}

			var worstGuard = (from guard in guardSleepTotals
							  orderby guard.Value descending
							  select guard.Key).First();

			var worstMinute = -1;

			for (var i = 0; i < 60; i++) {
				if (guardSleepMinutes[worstGuard][i] > worstMinute) {
					worstMinute = i;
				}
			}

			Console.WriteLine($"Guard {worstGuard} * Minute {worstMinute} = {worstGuard * worstMinute}");
		}

		public void Part2() {
			var guardSleepMinutes = LoadGuardSleepMinutes();

			var worstGuard = 0;
			var worstMinute = 0;
			var worstMinuteTotal = 0;

			foreach (var guard in guardSleepMinutes) {
				for (var i = 0; i < 60; i++) {
					if (guard.Value[i] > worstMinuteTotal) {
						worstMinuteTotal = guard.Value[i];
						worstMinute = i;
						worstGuard = guard.Key;
					}
				}
			}

			Console.WriteLine($"Guard {worstGuard} * Minute {worstMinute} = {worstGuard * worstMinute}");
		}

		Dictionary<int, int[]> LoadGuardSleepMinutes() {
			var logs = LoadLogs();

			var guardSleepMinutes = new Dictionary<int, int[]>();

			var currentGuard = 0;
			var sleepStart = 0;
			var sleepEnd = 0;

			foreach (var log in logs) {
				var match = Regex.Match(log.Event, @"Guard #(\d+)? begins shift");

				if (match.Success) {
					currentGuard = Convert.ToInt32(match.Groups[1].Value);

					if (!guardSleepMinutes.ContainsKey(currentGuard)) {
						guardSleepMinutes.Add(currentGuard, new int[60]);
					}
				}
				else if (log.Event == "falls asleep") {
					sleepStart = log.Timestamp.Minute;
				}
				else {
					sleepEnd = log.Timestamp.Minute;

					for (var i = sleepStart; i < sleepEnd; i++) {
						guardSleepMinutes[currentGuard][i]++;
					}
				}
			}

			return guardSleepMinutes;
		}

		List<Log> LoadLogs() {
			var input = File.ReadAllLines(INPUTFILE);

			var logs = new List<Log>();

			foreach (var line in input) {
				var match = Regex.Match(line, @"\[(?<datetime>\d{4}-\d{2}-\d{2} \d{2}:\d{2})] (?<event>.+)");

				if (!match.Success) {
					throw new Exception("Your regex is wrong");
				}

				var timestamp = DateTime.ParseExact(match.Groups["datetime"].Value, "yyyy-MM-dd H:mm", CultureInfo.InvariantCulture);
				logs.Add(new Log(timestamp, match.Groups["event"].Value));
			}

			return logs.OrderBy(l => l.Timestamp).ToList();
		}

		class Log {
			public DateTime Timestamp { get; set; }
			public string Event { get; set; }

			public Log(DateTime timestamp, string eventText) {
				Timestamp = timestamp;
				Event = eventText;
			}
		}
	}