Added unit test project for HelperClasses and tests for IntegerRange.cs. Implemented IEnumerable on IntegerRange.

AdventOfCode.HelperClasses/IntegerRange.cs

@@ -1,21 +1,23 @@
-namespace AdventOfCode.HelperClasses;
+using System.Collections;
 
-public record IntegerRange(long start, long end)
+namespace AdventOfCode.HelperClasses;
+
+public record IntegerRange(long start, long end) : IEnumerable<long>
 {
-    public long Count() => end - start + 1;
+    public long Count => end - start + 1;
 
     public bool Contains(long number) => start <= number && end >= number;
 
     public bool TryCombine(IntegerRange other, out IntegerRange combined)
     {
-        if (Contains(other.start))
+        if (Contains(other.start) || other.start == end + 1)
         {
             var isEndInRange = Contains(other.end);
             combined = isEndInRange ? this : this with {end = other.end};
             return true;
         }
         
-        if (other.Contains(start))
+        if (other.Contains(start) || start == other.end + 1)
         {
             var isEndInRange = other.Contains(end);
             combined = isEndInRange ? other : other with {end = end};
@@ -25,4 +27,34 @@ public record IntegerRange(long start, long end)
         combined = this;
         return false;
     }
+
+    public IEnumerator<long> GetEnumerator() => new IntegerRangeEnumerator(start, end);
+
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+}
+
+public record IntegerRangeEnumerator(long start, long end) : IEnumerator<long>
+{
+    private long _current = start - 1;
+
+    public bool MoveNext()
+    {
+        if(_current >= end) return false;
+        _current++;
+        return true;
+    }
+
+    public void Reset()
+    {
+        _current = start - 1;
+    }
+
+    long IEnumerator<long>.Current => _current;
+
+    object? IEnumerator.Current => _current;
+
+    public void Dispose()
+    {
+        GC.SuppressFinalize(this);
+    }
 }