Update 0779-k-th-symbol-in-grammar.java

Author: sujal-goswami

java/0779-k-th-symbol-in-grammar.java

@@ -1,15 +1,18 @@
-//Explanation: https://leetcode.com/problems/k-th-symbol-in-grammar/discuss/2174956/Easy-java-solution-or-Imagine-a-binary-tree. (Upvote if you liked!!)
-//Asked in: Google (lintcode)
-
 class Solution {
-
     public int kthGrammar(int n, int k) {
-        if (n == 1 || k == 1) return 0;
-        int prevK = (int) Math.pow(2, n - 2);
-        if (k <= prevK) return kthGrammar(n - 1, k); else {
-            int presK = k % prevK;
-            int val = kthGrammar(n - 1, presK == 0 ? k / 2 : k % prevK);
-            return val == 1 ? 0 : 1;
+        int left = 1;
+        int right = (int)Math.pow(2,n-1);
+        int cur = 0;
+
+        for(int i = 0; i < n-1; i++){
+            int mid = (left + right)/2;
+            if(k <= mid)
+                right = mid;
+            else{
+                left = mid + 1;
+                cur = (cur == 1)? 0: 1;
+            }    
         }
+        return cur;
     }
 }