fork(8) download
  1. #pragma GCC optimize("Ofast")
  2. #pragma GCC target("avx")
  3. #include <bits/stdc++.h>
  4. using pii = std::pair<int, int>;
  5. const int NMAX = (int)1e9;
  6. const int SNMAX = (int)sqrt(NMAX) + 1;
  7. std::bitset<NMAX + 1> bits;
  8. int main() {
  9. bits[0] = bits[1] = 1;
  10. std::vector<pii> smallPrimes;
  11. for (int i = 2; i <= SNMAX; ++i) {
  12. if (!bits[i]) {
  13. smallPrimes.push_back({i, i * i});
  14. for (int j = i * i; j <= SNMAX; j += i) {
  15. bits[j] = 1;
  16. }
  17. }
  18. }
  19. const int blockSize = 1 << 18;
  20. for (int from = 0; from <= NMAX; from += blockSize) {
  21. int to = std::min(from + blockSize - 1, NMAX);
  22. for (pii& p : smallPrimes) {
  23. for (; p.second <= to; p.second += p.first) bits[p.second] = 1;
  24. }
  25. }
  26. bits.flip();
  27. //iterate over primes
  28. int64_t sum(0);
  29. int cnt(0);
  30. for (int p = bits._Find_first(); p < bits.size(); p = bits._Find_next(p)) {
  31. sum += p;
  32. cnt++;
  33. }
  34. assert(bits.count() == cnt);
  35. std::cout << "sum = " << sum << std::endl;
  36. std::cout << "cnt = " << cnt << std::endl;
  37. return 0;
  38. }
Success #stdin #stdout 3.35s 125572KB
stdin
Standard input is empty
stdout
sum = 24739512092254535
cnt = 50847534