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Refactor `EnumerableExtensions` to simplify combination generation by removing `Range` method and streamlining index logic

This commit is contained in:
Sebastian Lindemeier 2025-12-15 10:44:38 +01:00
parent ee061757a8
commit 56521d39d7
1 changed files with 9 additions and 20 deletions
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29
AdventOfCode.Extensions/EnumerableExtensions.cs
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@ -12,29 +12,24 @@ public static class EnumerableExtensions
var poolLength = pool.Length; var poolLength = pool.Length;
if (count > poolLength) if (count > poolLength)
yield break; yield break;
var indices = Range(0, count).ToArray(); var indices = Enumerable.Range(0, count).ToArray();
yield return GetCombination(indices, pool); yield return GetCombination(indices, pool);
while (true) while (true)
{ {
var validIndex = false; int idx;
var currentIndex = 0; for(idx = count - 1; idx >= 0; idx--)
for(var i = count - 1; i >= 0; i--)
{ {
currentIndex = i; var isIndexBelowMax = indices[idx] != idx + poolLength - count;
if (indices[i] != i + poolLength - count) if (isIndexBelowMax)
{
validIndex = true;
break; break;
}
} }
if(!validIndex) if(idx < 0)
yield break; yield break;
indices[currentIndex] += 1; indices[idx] += 1;
foreach (var j in Range(currentIndex + 1, count)) for (var j = idx + 1; j < count; j++)
{ {
Index ix = j - 1; indices[j] = indices[j - 1] + 1;
indices[j] = indices[ix] + 1;
} }
yield return GetCombination(indices, pool); yield return GetCombination(indices, pool);
@ -42,11 +37,5 @@ public static class EnumerableExtensions
static TValue[] GetCombination(int[] innerIndices, TValue[] innerPool) => static TValue[] GetCombination(int[] innerIndices, TValue[] innerPool) =>
innerIndices.Select(i => innerPool[i]).ToArray(); innerIndices.Select(i => innerPool[i]).ToArray();
static IEnumerable<int> Range(int start, int end)
{
for (var i = start; i < end; i++)
yield return i;
}
} }
} }