Add Maximum Array Rotation in C# (#4876)

Author: pascalecu

archive/c/c-sharp/MaximumArrayRotation.cs

@@ -0,0 +1,72 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+
+public static class Program
+{
+    private static void ShowUsage()
+    {
+        Console.Error.WriteLine("Usage: please provide a list of integers (e.g. \"8, 3, 1, 2\")");
+        Environment.Exit(1);
+    }
+
+    private static List<int> ParseIntegerList(string input)
+    {
+        if (string.IsNullOrWhiteSpace(input))
+            ShowUsage();
+
+        var list = input
+            .Split(',', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries)
+            .Select(s =>
+            {
+                if (!int.TryParse(s, out var val) || val < 0)
+                    ShowUsage();
+                return val;
+            })
+            .ToList();
+
+        if (list.Count == 0)
+            ShowUsage();
+
+        return list;
+    }
+
+    private static int MaximumRotationSum(IList<int> numbers)
+    {
+        int n = numbers.Count;
+        if (n == 0)
+            ShowUsage();
+
+        int totalSum = 0;
+        int currentWeightedSum = 0;
+
+        for (int i = 0; i < n; i++)
+        {
+            totalSum += numbers[i];
+            currentWeightedSum += numbers[i] * i;
+        }
+
+        int maxWeightedSum = currentWeightedSum;
+
+        for (int i = 1; i < n; i++)
+        {
+            currentWeightedSum = currentWeightedSum + totalSum - n * numbers[n - i];
+            if (currentWeightedSum > maxWeightedSum)
+                maxWeightedSum = currentWeightedSum;
+        }
+
+        return maxWeightedSum;
+    }
+
+    public static int Main(string[] args)
+    {
+        if (args.Length != 1)
+            ShowUsage();
+
+        var inputList = ParseIntegerList(args[0]);
+
+        Console.WriteLine(MaximumRotationSum(inputList));
+
+        return 0;
+    }
+}