Sieve of Eratosthenes

Algorithm to obtain prime numbers from 1 to N.
(Regarded as the oldest algorithm in the world)

Author: aryansarkar13

sieve.cpp

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+#include <bits/stdc++.h> 
+using namespace std; 
+  
+void SieveOfEratosthenes(int n) 
+{ 
+    // Create a boolean array and initialize the values as true
+    bool prime[n+1]; 
+    memset(prime, true, sizeof(prime)); 
+  
+    for (int p=2; p*p<=n; p++) 
+    { 
+        // If prime[p] is not changed, then it is a prime 
+        if (prime[p] == true) 
+        { 
+            //Update multiples  
+            for (int i=p*p; i<=n; i += p) 
+                prime[i] = false; 
+        } 
+    } 
+  
+    // Print all prime numbers 
+    for (int p=2; p<=n; p++) 
+       if (prime[p]) 
+          cout << p << " "; 
+} 
+  
+// Driver Program
+int main() 
+{ 
+    int n = 30; 
+    cout << " Prime Numbers in the range 1 to " << n << endl; 
+    SieveOfEratosthenes(n); 
+    return 0; 
+}