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779.k-th-symbol-in-grammar.go
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779.k-th-symbol-in-grammar.go
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/*
* @lc app=leetcode id=779 lang=golang
*
* [779] K-th Symbol in Grammar
*
* https://leetcode.com/problems/k-th-symbol-in-grammar/description/
*
* algorithms
* Medium (36.97%)
* Likes: 346
* Dislikes: 121
* Total Accepted: 25.7K
* Total Submissions: 69.6K
* Testcase Example: '1\n1'
*
* 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)].
*
*
*/
package golang
// https://leetcode.com/problems/k-th-symbol-in-grammar/discuss/113697/My-3-lines-C%2B%2B-recursive-solution
// @lc code=start
func kthGrammar(N int, K int) int {
if N == 1 {
return 0
}
if K%2 == 0 {
return inverse(kthGrammar(N-1, K/2))
}
return kthGrammar(N-1, (K+1)/2)
}
func inverse(n int) int {
if n == 0 {
return 1
}
return 0
}
// @lc code=end