Create PrimeNumbers.cpp (#607)

* Create PrimeNumbers.cpp

* Rename Math/PrimeNumbers/PrimeNumbers.cpp to math/prime_numbers.cpp

* Trailing whitespace, std::cin, std::cout, std::endl

* std::vector

* std::vector again

math/prime_numbers.cpp

@@ -0,0 +1,26 @@
+#include <iostream>
+#include <vector>
+
+std::vector<int> primes(int max) {
+    max++;
+    std::vector<int> res;
+    std::vector<bool> numbers(max, false);
+    for (int i = 2; i < max; i++) {
+        if (!numbers[i]) {
+            for (int j = i; j < max; j += i)
+                numbers[j] = true;
+            res.push_back(i);
+        }
+    }
+    return res;
+}
+
+int main() {
+    std::cout << "Calculate primes up to:\n>> ";
+    int n;
+    std::cin >> n;
+    std::vector<int> ans = primes(n);
+    for (int i = 0; i < ans.size(); i++)
+        std::cout << ans[i] << ' ';
+    std::cout << std::endl;
+}