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  1. #include <bits/stdc++.h>
  2. using namespace std;
  3.  
  4. const int MAXPR = (int)1e8;
  5. void calcPrimes() {
  6. auto sum = 2LL;
  7. int cnt = 1;
  8.  
  9. const int S = round(sqrt(MAXPR));
  10. vector<char> sieve(S + 1, true);
  11. vector<array<int, 2>> cp;
  12. for (int i = 3; i < S; i += 2) {
  13. if (!sieve[i])
  14. continue;
  15. cp.push_back({i, (i * i - 1) / 2});
  16. for (int j = i * i; j <= S; j += 2 * i)
  17. sieve[j] = false;
  18. }
  19. vector<char> block(S);
  20. int high = (MAXPR - 1) / 2;
  21. for (int low = 0; low <= high; low += S) {
  22. fill(block.begin(), block.end(), true);
  23. for (auto &i : cp) {
  24. int p = i[0], idx = i[1];
  25. for (; idx < S; idx += p)
  26. block[idx] = false;
  27. i[1] = idx - S;
  28. }
  29. if (low == 0)
  30. block[0] = false;
  31. for (int i = 0; i < S && low + i <= high; i++)
  32. if (block[i])
  33. ++cnt, sum += (low + i) * 2 + 1;
  34. };
  35.  
  36. cout << "sum = " << sum << endl;
  37. cout << "cnt = " << cnt << endl;
  38. }
  39.  
  40. int main() {
  41. calcPrimes();
  42. return 0;
  43. }
Success #stdin #stdout 0.14s 4528KB
stdin
Standard input is empty
stdout
sum = 279209790387276
cnt = 5761455