Create 0779-k-th-symbol-in-grammar.kt

Author: a93a

kotlin/0779-k-th-symbol-in-grammar.kt

@@ -0,0 +1,33 @@
+class Solution {
+    fun kthGrammar(n: Int, k: Int): Int {
+        var cur = 0
+        var left = 1
+        var right = 2.0.pow(n - 1).toInt()
+
+        repeat (n - 1) {
+            val mid = (left + right) / 2
+            if (k <= mid) {
+                right = mid
+            } else {
+                left = mid + 1
+                cur = if (cur == 1) 0 else 1
+            }
+        }
+
+        return cur
+    }
+}
+
+// another solution using the same thought but different way of coding it
+class Solution {
+    fun kthGrammar(n: Int, k: Int): Int {
+        if (n == 1) return 0
+        if (k % 2 == 0) return if (kthGrammar(n - 1,  k / 2) == 0) 1 else 0
+        else return if (kthGrammar(n - 1, (k + 1) / 2) == 0) 0 else 1
+    }
+}
+
+// another solution, recommend reading https://leetcode.com/problems/k-th-symbol-in-grammar/solutions/113705/java-one-line/ for explanation
+class Solution {
+    fun kthGrammar(n: Int, k: Int) = Integer.bitCount(k - 1) and 1
+}