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  • [leetcode-779-K-th Symbol in Grammar]

    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:

    1. N will be an integer in the range [1, 30].
    2. K will be an integer in the range [1, 2^(N-1)].

    思路:

    递归即可,判断当前的k是奇数还是偶数,如果是偶数,那么再查看上一行是1还是0即可。k是奇数同理。

    int kthGrammar(int N, int K) {
          if(N ==  1) return  0;
          if(K % 2 == 0) return (kthGrammar(N - 1, K / 2) == 0) ? 1 : 0;
          else   return (kthGrammar(N - 1, (K+1) / 2) == 0) ? 0 : 1; 
        }
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  • 原文地址:https://www.cnblogs.com/hellowooorld/p/8437948.html
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