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  1. import java.util.ArrayList;
  2. import java.util.List;
  3.  
  4. public class Main {
  5.  
  6.     // Function to find all prime numbers up to n using Sieve of Eratosthenes
  7.     public static List<Integer> sieve(int n) {
  8.         // Create a boolean array prime[0..n] and initialize all entries as true
  9.         boolean[] prime = new boolean[n + 1];
  10.         for (int i = 0; i <= n; i++) {
  11.             prime[i] = true; // Assume all numbers are prime initially
  12.         }
  13.  
  14.         // 0 and 1 are not prime numbers
  15.         prime[0] = false;
  16.         prime[1] = false;
  17.  
  18.         // Only need to check numbers up to sqrt(n)
  19.         int limit = (int) Math.sqrt(n);
  20.  
  21.         // Mark multiples of each prime as not prime
  22.         for (int p = 2; p <= limit; p++) {
  23.             if (prime[p]) { // If p is prime
  24.                 for (int i = p * p; i <= n; i += p) { // Mark multiples
  25.                     prime[i] = false;
  26.                 }
  27.             }
  28.         }
  29.  
  30.         // Collect all prime numbers into a list
  31.         List<Integer> primes = new ArrayList<>();
  32.         for (int i = 0; i <= n; i++) {
  33.             if (prime[i]) {
  34.                 primes.add(i);
  35.             }
  36.         }
  37.  
  38.         return primes; // Return all primes up to n
  39.     }
  40.  
  41.     // Function to find prime numbers in a specific range [start, end]
  42.     public static List<Integer> sieveRange(int start, int end) {
  43.         // Step 1: Find all primes up to 'end'
  44.         List<Integer> primes = sieve(end);
  45.  
  46.         // Step 2: Create a list to store primes in the range [start, end]
  47.         List<Integer> rangePrimes = new ArrayList<>();
  48.  
  49.         // Step 3: Filter primes that are >= start
  50.         for (int prime : primes) {
  51.             if (prime >= start) {
  52.                 rangePrimes.add(prime);
  53.             }
  54.         }
  55.  
  56.         return rangePrimes; // Return primes in the desired range
  57.     }
  58.  
  59.     public static void main(String[] args) {
  60.         int l = 1;   // Start of the range
  61.         int r = 100; // End of the range
  62.  
  63.         // Get all prime numbers in the range [l, r]
  64.         List<Integer> primesInRange = sieveRange(l, r);
  65.  
  66.         // Print all prime numbers in the range
  67.         System.out.println("Prime numbers between " + l + " and " + r + " are:");
  68.         for (int prime : primesInRange) {
  69.             System.out.println(prime);
  70.         }
  71.     }
  72. }
  73.  
Success #stdin #stdout 0.16s 57872KB
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Standard input is empty
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Prime numbers between 1 and 100 are:
2
3
5
7
11
13
17
19
23
29
31
37
41
43
47
53
59
61
67
71
73
79
83
89
97
https://ideone.com/O7xrEl
language:
Java (HotSpot 12)
created:
4 days ago
visibility:
public

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