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  1. #include <iostream>
  2. #include <math.h>
  3. using namespace std;
  4.  
  5. const int MAXN = 1e7;
  6. int prime[MAXN]; // Array to store prime status of numbers up to 10^7
  7.  
  8. void sieve() {
  9.     // Step 1: Assume all numbers are prime
  10.     for (int i = 0; i <= MAXN; i++) {
  11.         prime[i] = 1;
  12.     }
  13.  
  14.     // Step 2: Mark 0 and 1 as non-prime
  15.     prime[0] = prime[1] = 0;
  16.  
  17.     // Step 3: Sieve process
  18.     for (int i = 2; i <= sqrt(MAXN); i++) {
  19.         if (prime[i]) { // If i is still prime
  20.             for (int j = i * i; j <= MAXN; j += i) {
  21.                 prime[j] = 0; // Mark multiples of i as non-prime
  22.             }
  23.         }
  24.     }
  25. }
  26.  
  27. int main() {
  28.     sieve();
  29.     int n;
  30.     cin >> n;
  31.     // Print prime numbers up to n 
  32.     for (int i = 0; i <= n; i++) {
  33.         if (prime[i]) {
  34.             cout << i << " ";
  35.         }
  36.     }
  37.  
  38.     return 0;
  39. }
  40.  
Success #stdin #stdout 0.13s 42516KB
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https://ideone.com/VryznY
List (count) the prime numbers in the range from 1 to 𝑁 (𝑁 ≤ 10^7)
language:
C++ (gcc 8.3)
created:
22 hours ago
visibility:
public

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