From 56521d39d74a9e16d31facea8a3459dddf4159e2 Mon Sep 17 00:00:00 2001
From: Sebastian Lindemeier <lindemeier.sebastian@bgetem.de>
Date: Mon, 15 Dec 2025 10:44:38 +0100
Subject: [PATCH] Refactor `EnumerableExtensions` to simplify combination
 generation by removing `Range` method and streamlining index logic

---
 .../EnumerableExtensions.cs                   | 29 ++++++-------------
 1 file changed, 9 insertions(+), 20 deletions(-)

diff --git a/AdventOfCode.Extensions/EnumerableExtensions.cs b/AdventOfCode.Extensions/EnumerableExtensions.cs
index c7dd053..76244ee 100644
--- a/AdventOfCode.Extensions/EnumerableExtensions.cs
+++ b/AdventOfCode.Extensions/EnumerableExtensions.cs
@@ -12,29 +12,24 @@ public static class EnumerableExtensions
         var poolLength = pool.Length;
         if (count > poolLength)
             yield break;
-        var indices = Range(0, count).ToArray();
+        var indices = Enumerable.Range(0, count).ToArray();
         yield return GetCombination(indices, pool);
         while (true)
         {
-            var validIndex = false;
-            var currentIndex = 0;
-            for(var i = count - 1; i >= 0; i--)
+            int idx;
+            for(idx = count - 1; idx >= 0; idx--)
             {
-                currentIndex = i;
-                if (indices[i] != i + poolLength - count)
-                {
-                    validIndex = true;
+                var isIndexBelowMax = indices[idx] != idx + poolLength - count;
+                if (isIndexBelowMax) 
                     break;
-                }
             }
-            if(!validIndex)
+            if(idx < 0)
                 yield break;
             
-            indices[currentIndex] += 1;
-            foreach (var j in Range(currentIndex + 1, count))
+            indices[idx] += 1;
+            for (var j = idx + 1; j < count; j++)
             {
-                Index ix = j - 1;
-                indices[j] = indices[ix] + 1;
+                indices[j] = indices[j - 1] + 1;
             }
 
             yield return GetCombination(indices, pool);
@@ -42,11 +37,5 @@ public static class EnumerableExtensions
 
         static TValue[] GetCombination(int[] innerIndices, TValue[] innerPool) => 
             innerIndices.Select(i => innerPool[i]).ToArray();
-
-        static IEnumerable<int> Range(int start, int end)
-        {
-            for (var i = start; i < end; i++)
-                yield return i;
-        }
     }
 }
\ No newline at end of file