-
Notifications
You must be signed in to change notification settings - Fork 2
/
KthSymbolInGrammar.java
57 lines (51 loc) · 1.36 KB
/
KthSymbolInGrammar.java
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
package Leetcode;
/**
* @author kalpak
*
* On the first row, we write a 0. 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.
*
* Given row N and index K, return the K-th indexed symbol in row N. (The values of K are 1-indexed.) (1 indexed).
*
* Examples:
* Input: N = 1, K = 1
* Output: 0
*
* Input: N = 2, K = 1
* Output: 0
*
* Input: N = 2, K = 2
* Output: 1
*
* Input: N = 4, K = 5
* Output: 1
*
* Explanation:
* row 1: 0
* row 2: 01
* row 3: 0110
* row 4: 01101001
* Note:
*
* N will be an integer in the range [1, 30].
* K will be an integer in the range [1, 2^(N-1)].
*
*/
public class KthSymbolInGrammar {
public static int kthGrammar(int N, int K) {
if(N == 1 && K == 1)
return 0;
// Calculate the length of every row which is as below.
// Length of each row is 2^(N - 1).
int mid = (int)Math.pow(2,N-1)/2;
// If the K lies in the first half, it is actually same as prev row
if(K <= mid)
return kthGrammar(N-1, K);
else
// Else it subtract the first half and then it is same as
// complement of the prev row
return kthGrammar(N-1, K - mid) ^ 1;
}
public static void main(String[] args) {
System.out.println(kthGrammar(4, 5));
}
}