Add files via upload

Seive of Eratosthenes is a concept mainly to find the prime number in given range in time complexity of O(loglogn) inspite of O(n^2). In this approach, we just mark all elements as prime and then we unmark them as they are divided and elements left at last are all prime numbers.

Author: DeependraParmar

18_seiveofEratosthenes.cpp

@@ -0,0 +1,28 @@
+#include <iostream>
+using namespace std;
+void seiveOfEratosthenes(int n){
+    int *a = new int[n]{0};
+    for(int i=2; i<=n; i++){
+        if(a[i] == 0){
+            for(int j=i*i; j<=n; j+=i){
+                a[j] = 1;
+            }
+        }
+    }
+    for(int i=2; i<=n; i++){
+        if(a[i]==0){
+            cout<<i<<" ";
+        }
+    }
+}
+int main(){
+    // Seive of Eratosthenes is a concept mainly to find the prime number in given range in time complexity of O(loglogn) inspite of O(n^2). In this approach, we just mark all elements as prime and then we unmark them as they are divided and elements left at last are all prime numbers. 
+    int n;
+    cout<<"Enter the value of n upto which prime numbers are to be printed: ";
+    cin>>n;
+
+    seiveOfEratosthenes(n);
+
+
+    return 0;
+}