31 lines
1.0 KiB
C++
31 lines
1.0 KiB
C++
#include <cstdio>
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/**
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* 779. K-th Symbol in Grammar
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* 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.
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* - For example, for n = 3, the 1st row is 0, the 2nd row is 01, and the 3rd row is 0110.
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* Given two integer n and k, return the kth (1-indexed) symbol in the nth row of a table of n rows.
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*/
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class Solution {
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public:
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static int kthGrammar(int n, int k) {
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--k;
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int cur = 0;
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while (--n)
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cur ^= !!(k & (1 << (n - 1)));
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return cur;
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}
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};
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int main() {
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std::printf("%d\n", Solution::kthGrammar(1, 1));
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std::printf("%d\n", Solution::kthGrammar(2, 1));
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std::printf("%d\n", Solution::kthGrammar(2, 2));
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std::printf("%d\n", Solution::kthGrammar(3, 1));
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std::printf("%d\n", Solution::kthGrammar(3, 2));
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std::printf("%d\n", Solution::kthGrammar(3, 3));
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std::printf("%d\n", Solution::kthGrammar(3, 4));
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return 0;
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}
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