26 lines
714 B
C++
26 lines
714 B
C++
pair<vector<int>, vector<int>> factcount(int n) {
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vector<bool> not_prime(n + 1);
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vector<int> res(n + 1), num(n + 1);
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vector<int> primes;
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res[1] = 1;
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for (int i = 2; i <= n; ++i) {
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if (not not_prime[i]) {
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res[i] = 2;
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num[i] = 1;
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primes.emplace_back(i);
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}
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for (auto&& x : primes) {
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if (i * x > n) break;
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not_prime[i * x] = 1;
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if (i % x == 0) {
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num[i * x] = num[i] + 1;
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res[i * x] = res[i] / num[i * x] * (num[i * x] + 1);
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break;
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}
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num[i * x] = 1;
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res[i * x] = res[i] * 2;
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}
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}
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return {primes, res};
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}
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