Create sieve.cpp

Language/C++/sieve.cpp

@@ -0,0 +1,34 @@
+//Printing the prime numbers upto a given number 'n' in O(n log log n) time.
+// as it takes O(n) time in iterartive method.
+#include <iostream>
+#include <string.h>
+using namespace std;
+int main()
+{
+    int n;
+    cin >> n;
+    int arr[n + 1];
+    memset(arr, 0, sizeof(arr));
+    arr[0] = 1;
+    arr[1] = 1;
+    for (int i = 2; i <= n; i++)
+    {
+        if (arr[i] == 0)
+        {
+            for (int j = 2; j <= n / i; j++)
+            {
+                if (arr[i * j] != 1)
+                {
+                    arr[i * j] = 1;
+                }
+            }
+        }
+    }
+    for (int i = 0; i <= n; i++)
+    {
+        if (arr[i] == 0)
+        {
+            cout << i << " ";
+        }
+    }
+}