Create Lecture - 24.cpp

Author: Prince-1501

Lecture - 24.cpp

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+//
+//  main.cpp
+//  Lecture - 24
+//
+//  Created by Prince  Kumar on 28/03/19.
+//  Copyright © 2019 Prince  Kumar. All rights reserved.
+//  seive of eratosthenes -- //
+
+#include <iostream>
+#include <cstring>
+using namespace std;
+
+void seive( int n)
+{
+    // create boolean array
+    bool prime[n+1];
+    memset(prime, true ,sizeof(prime));
+    
+    for(int p=2;p*p<=n;p++)
+    {
+        //  if prime[p] --> false  --> it is not prime
+        if(prime[p]==true)
+        {
+            for(int i=p*p;i<=n;i=i+p)
+            {
+                prime[i]=false;
+            }
+        }
+    }
+    
+    // print prime numbers
+    for(int j=2;j<=n;j++)
+    {
+        if(prime[j]==true)
+            cout<<j<<endl;
+    }
+}
+int main()
+{
+    cout <<"Enter number upto which you want to print prime numbers "<<endl;
+    int n ; cin>>n;
+    seive(n);
+}