Ejemplo n.º 1
0
        public static long Part2(IEnumerable <string> busIds)
        {
            if (busIds == null)
            {
                throw new ArgumentNullException(nameof(busIds));
            }

            IEnumerable <(long, int)> validBusIdsWithIndexes = busIds
                                                               .Select((busId, i) => (busId, i))
                                                               .Where(t => t.Item1 != "x")
                                                               .Select(t => (long.Parse(t.Item1, CultureInfo.InvariantCulture), t.Item2));

            return(ChineseRemainderTheorem.Solve(
                       validBusIdsWithIndexes.Select(t => t.Item1).ToArray(),
                       validBusIdsWithIndexes.Select(t => t.Item1 - t.Item2).ToArray()
                       ));
        }
Ejemplo n.º 2
0
        static long Part2(string[] lines)
        {
            int i = -1;
            List <Congruence> congruences = new List <Congruence>();

            foreach (var l in lines[1].Split(','))
            {
                i++;
                if (l == "x")
                {
                    continue;
                }
                int m = int.Parse(l);
                congruences.Add(new Congruence(m - i, int.Parse(l)));
            }
            return(ChineseRemainderTheorem.Solve(congruences));
        }
Ejemplo n.º 3
0
        static void Main(string[] args)
        {
            var input  = File.ReadAllLines("Input.txt");
            int time   = Convert.ToInt32(input[0]);
            var busses = new List <int>();

            foreach (var bus in input[1].Split(','))
            {
                if (Int32.TryParse(bus, out int busnum))
                {
                    busses.Add(busnum);
                }
            }
            var nextBus = (from busNumber in busses
                           select(Number: busNumber, Time: GetNextBusTime(time, busNumber)))
                          .OrderBy(x => x.Time).First();
            var part1Answer = (nextBus.Time - time) * nextBus.Number;

            Console.WriteLine($"Part1: {part1Answer}");

            // Part2: Notes
            // Start at first bus arrival from index 1. This is `t`
            // Take the next bus, look up the index. Figure out if t + index is divisible by busNumber
            //    If true, keep going untill all numbers are exhausted
            //          Recursion? -- No.
            //    If false increment t by first bus number and try again
            // Forget all above, use chinese remained theroem copypasta
            var valueOffset = input[1].Split(',')
                              .Select((value, offset) => (value, offset))
                              .Where(x => x.value != "x")
                              .Select(x => (Value: Convert.ToInt64(x.value), Offset: x.offset));
            var n = valueOffset.Select(x => x.Value).ToArray();
            var a = valueOffset.Select(x => x.Value - x.Offset).ToArray();

            a[0] = 0;
            var part2Answer = ChineseRemainderTheorem.Solve(n, a);

            Console.WriteLine($"Part2: {part2Answer}");
        }