Data commit

Task/Generate-Chess960-starting-position/Kotlin/generate-chess960-starting-position.kotlin

@@ -0,0 +1,30 @@
+object Chess960 : Iterable<String> {
+    override fun iterator() = patterns.iterator()
+
+    private operator fun invoke(b: String, e: String) {
+        if (e.length <= 1) {
+            val s = b + e
+            if (s.is_valid()) patterns += s
+        } else {
+            for (i in 0 until e.length) {
+                invoke(b + e[i], e.substring(0, i) + e.substring(i + 1))
+            }
+        }
+    }
+
+    private fun String.is_valid(): Boolean {
+        val k = indexOf('K')
+        return indexOf('R') < k && k < lastIndexOf('R') &&
+            indexOf('B') % 2 != lastIndexOf('B') % 2
+    }
+
+    private val patterns = sortedSetOf<String>()
+
+    init {
+        invoke("", "KQRRNNBB")
+    }
+}
+
+fun main(args: Array<String>) {
+    Chess960.forEachIndexed { i, s -> println("$i: $s") }
+}