Use substring iterator directly

2024/src/main/kotlin/Grid.kt

@@ -13,11 +13,9 @@ class Grid(val rows: List<String>) {
     fun chars(x: Int, y: Int, dx: Int, dy: Int) = Line(x, y, dx, dy)
 
     inner class Line(val x: Int, val y: Int, val dx: Int, val dy: Int) : Sequence<Char> {
-        override fun iterator(): Iterator<Char> = iterator {
-            if (dx == 1 && dy == 0) {
-                yieldAll(rows[y].substring(startIndex = x).asSequence())
-            } else {
-
+        override fun iterator(): Iterator<Char> = if (dx == 1 && dy == 0) {
+            rows[y].substring(startIndex = x).iterator()
+        } else iterator {
             var x = x
             var y = y
 
@@ -28,7 +26,7 @@ class Grid(val rows: List<String>) {
             }
         }
     }
-    }
+
 
     fun rows(): Sequence<Line> = sequence {
         for (y in 0..<height) {