35 lines
682 B
C++
35 lines
682 B
C++
#include <iostream>
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#include <unordered_set>
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class Solution {
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public:
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static int smallestRepunitDivByK(int k) {
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if (k == 1) return 1;
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/*
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* Bad code.
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* Despite std::unordered_set is O(1),
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* it increases space complexity
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* and the constant increases.
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int pos = 2, rem = 11 % k;
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std::unordered_set<int> s;
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s.insert(rem);
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while (true) {
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if (!rem)
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return pos;
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rem = (10 * rem + 1) % k;
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++pos;
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if (s.count(rem))
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return -1;
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s.insert(rem);
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}
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*/
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for (int pos = 1, rem = 1; pos < k; ++pos)
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if (!(rem = (10 * rem + 1) % k))
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return ++pos;
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return -1;
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}
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};
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int main() {
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std::printf("%d\n", Solution::smallestRepunitDivByK(7));
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} |