TWC198

1 files changed, 30 insertions, 0 deletions

diff --git a/challenge-198/deadmarshal/cpp/ch-2.cpp b/challenge-198/deadmarshal/cpp/ch-2.cpp
new file mode 100644
index 0000000000..adfcbd6a20
--- /dev/null
+++ b/challenge-198/deadmarshal/cpp/ch-2.cpp
@@ -0,0 +1,30 @@
+#include<iostream>
+
+bool is_prime(int n)
+{
+  int i = 5;
+  if((n == 2) || (n == 3)) return true;
+  if((n <= 1) || (n % 2 == 0) || (n % 3 == 0)) return false;
+  while(i * i <= n)
+  {
+    if((n % i == 0) || (n % (i+2) == 0)) return false;
+    i += 6;
+  }
+  return true;
+}
+
+int prime_count(int n)
+{
+  int count = 0;
+  for(int i = 1; i < n; ++i) if(is_prime(i)) count++;
+  return count;
+}
+
+int main()
+{
+  std::cout << prime_count(10) << '\n';
+  std::cout << prime_count(15) << '\n';
+  std::cout << prime_count(1) << '\n';
+  std::cout << prime_count(25) << '\n';
+}
+