Extract Combinations method to AdventOfCode.Extensions and refactor usages to improve modularity and reduce duplication

AoC_2025/Day10.cs

@@ -6,6 +6,7 @@ using System.Data.Common;
 using System.IO;
 using System.Linq;
 using AdvenOfCode.Contracts;
+using AdventOfCode.Extensions;
 using Microsoft.Z3;
 
 namespace AoC_2025;
@@ -214,7 +215,7 @@ public class Day10 : IPuzzleSolver<long>
         yield return ([..Enumerable.Repeat(0, patternLength)], 0);
         for (var i = 1; i <= buttons.Length; i++)
         {
-            foreach (var buttonPattern in Combinations(buttons, i))
+            foreach (var buttonPattern in buttons.Combinations(i))
             {
                 var joltageLevels = GetJoltageLevelsForButtonPattern(patternLength, buttonPattern);
                 yield return (joltageLevels, buttonPattern.Length);
@@ -271,50 +272,6 @@ public class Day10 : IPuzzleSolver<long>
         var answer = answerExpression is IntNum number ? number.Int64 : 0;
         return answer;
     }
-    
-    private IEnumerable<TValue[]> Combinations<TValue>(IEnumerable<TValue> values, int count)
-    {
-        var pool = values.ToArray();
-        var poolLength = pool.Length;
-        if (count > poolLength)
-            yield break;
-        var indices = Range(0, count).ToArray();
-        yield return GetCombination(indices, pool);
-        while (true)
-        {
-            var validIndex = false;
-            var currentIndex = 0;
-            foreach (var i in Range(0, count).Reverse())
-            {
-                currentIndex = i;
-                if (indices[i] != i + poolLength - count)
-                {
-                    validIndex = true;
-                    break;
-                }
-            }
-            if(!validIndex)
-                yield break;
-            
-            indices[currentIndex] += 1;
-            foreach (var j in Range(currentIndex + 1, count))
-            {
-                Index ix = j - 1;
-                indices[j] = indices[ix] + 1;
-            }
-
-            yield return GetCombination(indices, pool);
-        }
-
-        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;
-        }
-    }
 }
 
 public class IntArrayEqualityComparer : IEqualityComparer<int[]>