chore(*): Move old solutions into a separate folder

old/2021/07/Program.cs

@@ -0,0 +1,79 @@
+namespace Day07
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            string input = File.ReadAllLines("input.txt")[0];
+            List<int> initialCrabPositions = input.Split(',').Select(int.Parse).ToList();
+
+            //Part1(initialCrabPositions);
+            Part2(initialCrabPositions);
+        }
+
+        static void Part1(List<int> initialCrabPositions)
+        {
+            // double mean = initialCrabPositions.Average();
+
+            // int meanAverage = Convert.ToInt32(mean);
+
+            int medianAverage = initialCrabPositions.OrderBy(x=>x).Skip(initialCrabPositions.Count()/2).First();
+
+            // int modalAverage = initialCrabPositions.GroupBy(n=> n).
+            //     OrderByDescending(g=> g.Count()).
+            //     Select(g => g.Key).FirstOrDefault();
+
+            // Console.WriteLine($"Mean average: {meanAverage}");
+            Console.WriteLine($"Median average: {medianAverage}");
+            // Console.WriteLine($"Modal average: {modalAverage}");
+
+            int totalFuelConsumption = 0; 
+
+            foreach (int position in initialCrabPositions)
+            {
+                // Find the difference
+                totalFuelConsumption += Math.Abs(position - medianAverage);
+            }
+
+            Console.WriteLine($"Total fuel consumption: {totalFuelConsumption}");
+        }
+
+        static void Part2(List<int> initialCrabPositions)
+        {
+            // Calculate optimal position 
+            // Loop through all possible positions and work out the total fuel consumption
+            int minPosition = initialCrabPositions.Min();
+            int maxPosition = initialCrabPositions.Max();
+
+            Dictionary<int, int> possiblePositions = new Dictionary<int, int>();
+
+            for (int i = minPosition; i <= maxPosition; i++)
+            {
+                possiblePositions.Add(i,CalculateTotalFuelConsumption(initialCrabPositions, i));
+            }
+
+            // Find lowest fuel consumption
+            var lowestFuelConsumptionPosition = possiblePositions.OrderBy(kvp => kvp.Value).First();
+            Console.WriteLine($"Position: {lowestFuelConsumptionPosition.Key} Fuel consumption: {lowestFuelConsumptionPosition.Value}");
+        }
+
+        public static int CalculateTotalFuelConsumption(List<int> initialCrabPositions, int targetPosition)
+        {
+            int totalFuelConsumption = 0; 
+
+            foreach (int position in initialCrabPositions)
+            {
+                // Find the difference
+                int difference = Math.Abs(position - targetPosition);
+                totalFuelConsumption += Convert.ToInt32(GetTriangularNumber(difference));
+            }
+
+            return totalFuelConsumption;
+        }
+
+        public static double GetTriangularNumber(int n)
+        {
+            return n*(n + 1) / 2;
+        }
+    }
+}