Add Zeckendorf in C#

archive/c/c-sharp/Zeckendorf.cs

@@ -0,0 +1,52 @@
+using System.Globalization;
+
+public static class Zeckendorf
+{
+    private static readonly long[] Fibs = GenerateFibs();
+
+    private static long[] GenerateFibs()
+    {
+        var fs = new List<long> { 1, 2 };
+        while (long.MaxValue - fs[^1] >= fs[^2])
+        {
+            fs.Add(fs[^1] + fs[^2]);
+        }
+        return [.. fs];
+    }
+
+    public static void Main(string[] args)
+    {
+        if (args.Length == 0 || !long.TryParse(args[0], NumberStyles.None, CultureInfo.InvariantCulture, out var n) || n < 0)
+        {
+            Console.WriteLine("Usage: please input a non-negative integer");
+            return;
+        }
+
+        if (n == 0) return;
+
+        Span<long> terms = stackalloc long[Fibs.Length];
+        int count = Decompose(n, terms);
+
+        PrintResults(terms[..count]);
+    }
+
+    private static int Decompose(long n, Span<long> terms)
+    {
+        int count = 0;
+        int i = Array.BinarySearch(Fibs, n);
+        if (i < 0) i = ~i - 1;
+
+        for (; i >= 0 && n > 0; i--)
+        {
+            if (Fibs[i] <= n)
+            {
+                terms[count++] = Fibs[i];
+                n -= Fibs[i];
+            }
+        }
+        return count;
+    }
+
+    private static void PrintResults(ReadOnlySpan<long> terms) =>
+        Console.WriteLine(string.Join(", ", terms.ToArray()));
+}