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5kyu(cpp): add „(Ready for) Prime Time“
Signed-off-by: Matej Focko <mfocko@redhat.com>
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5kyu/prime_time/solution.cpp
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63
5kyu/prime_time/solution.cpp
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#include <cassert>
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#include <vector>
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namespace {
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inline std::size_t index(unsigned p) { return p - 2; }
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inline bool is_prime(const std::vector<bool> &primes, unsigned p) {
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return primes[index(p)];
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}
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void discard_multiples(std::vector<bool> &primes, unsigned p) {
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for (auto k = 2; index(p * k) < primes.size(); k++) {
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primes[index(p * k)] = false;
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}
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}
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void discard_even(std::vector<bool> &primes) { discard_multiples(primes, 2); }
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std::vector<unsigned> construct_primes(const std::vector<bool> &primes) {
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std::vector<unsigned> result;
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for (auto p = 0u; p < primes.size(); p++) {
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if (primes[p]) {
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result.push_back(p + 2);
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}
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}
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return result;
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}
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} // namespace
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// Generate an array containing every prime number between 0 and the num
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// specified (inclusive)
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std::vector<unsigned> prime(unsigned n) {
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if (n < 2) {
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return {};
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}
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std::vector<bool> primes(n - 1, true);
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discard_even(primes);
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for (auto p = 3u; p <= n; p += 2) {
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if (!is_prime(primes, p)) {
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continue;
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}
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discard_multiples(primes, p);
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}
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return construct_primes(primes);
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}
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int main() {
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assert(prime(0) == std::vector<unsigned>{});
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assert(prime(1) == std::vector<unsigned>{});
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assert(prime(2) == std::vector<unsigned>{2});
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assert((prime(23) == std::vector<unsigned>{2, 3, 5, 7, 11, 13, 17, 19, 23}));
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assert(
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(prime(30) == std::vector<unsigned>{2, 3, 5, 7, 11, 13, 17, 19, 23, 29}));
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return 0;
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}
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@ -98,6 +98,7 @@
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- [Greed is Good](https://www.codewars.com/kata/5270d0d18625160ada0000e4) - [solution](5kyu/greed_is_good)
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- [Greed is Good](https://www.codewars.com/kata/5270d0d18625160ada0000e4) - [solution](5kyu/greed_is_good)
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- [Snakes and Ladders](https://www.codewars.com/kata/587136ba2eefcb92a9000027) - [solution](5kyu/snakes_and_ladders)
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- [Snakes and Ladders](https://www.codewars.com/kata/587136ba2eefcb92a9000027) - [solution](5kyu/snakes_and_ladders)
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- [The Clockwise Spiral](https://www.codewars.com/kata/536a155256eb459b8700077e) - [solution](5kyu/the_clockwise_spiral)
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- [The Clockwise Spiral](https://www.codewars.com/kata/536a155256eb459b8700077e) - [solution](5kyu/the_clockwise_spiral)
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- [(Ready for) Prime Time](https://www.codewars.com/kata/521ef596c106a935c0000519) - [solution](5kyu/prime_time)
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### Python
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### Python
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