Merge pull request #234 from the-hdr/main

Add sieve_of_eratosthenes.cpp

Author: kaal-coder

Coding/sieve_of_eratosthenes.cpp

@@ -0,0 +1,43 @@
+#include <iostream>
+#include <vector>
+
+using namespace std;
+
+void sieve (vector<bool>& isPrime)
+{
+    int upperLimit = isPrime.size() - 1;
+    
+    isPrime[0] = isPrime[1] = false;
+    for (int i = 2; i*i <= upperLimit; ++i)
+    {
+        if (isPrime[i]) 
+        {
+            for (int j = i*i; j <= upperLimit; j += i)
+            {
+                isPrime[j] = false;
+            }
+        }
+    }
+}
+
+int main()
+{
+    cout << "Enter the number till which you want to know all the primes: ";
+    int userInput;
+    cin >> userInput;
+    
+    vector<bool> isPrime (userInput + 1, true);
+    sieve (isPrime);
+    
+    cout << "All the primes till " << userInput << ": " << endl;
+    for (int currentNumber = 2; currentNumber <= userInput; ++currentNumber)
+    {
+        if (isPrime[currentNumber])
+        {
+            cout << currentNumber << ' ';
+        }
+    }
+    cout << endl;
+    
+    return 0;
+}