LeetCode in Kotlin
779. K-th Symbol in Grammar
Medium
We build a table of n rows (1-indexed). We start by writing 0 in the 1st row. Now in every subsequent row, we look at the previous row and replace each occurrence of 0 with 01, and each occurrence of 1 with 10.
- For example, for
n = 3, the1strow is0, the2ndrow is01, and the3rdrow is0110.
Given two integer n and k, return the kth (1-indexed) symbol in the nth row of a table of n rows.
Example 1:
Input: n = 1, k = 1
Output: 0
Explanation: row 1: 0
Example 2:
Input: n = 2, k = 1
Output: 0
Explanation: row 1: 0 row 2: 01
Example 3:
Input: n = 2, k = 2
Output: 1
Explanation: row 1: 0 row 2: 01
Constraints:
1 <= n <= 301 <= k <= 2n - 1
Solution
class Solution {
/*
* Time: O(logn)
* Space: O(1)
*/
fun kthGrammar(n: Int, k: Int): Int {
return Integer.bitCount(k - 1) % 2 + n - n
}
}