compile_time_power_of_number.cpp

puzzles/interviews/training/compile_time_power_of_number.cpp

@@ -0,0 +1,89 @@
+/*
+VIM: let b:lcppflags="-std=c++14 -O2 -pthread -I."
+VIM: let b:wcppflags="/O2 /EHsc /DWIN32"
+VIM-: let b:cppflags=g:Iboost.g:Itbb
+VIM-: let b:ldflags=g:Lboost.g:Ltbb
+VIM-: let b:ldlibpath=g:Bboost.g:Btbb
+VIM-: let b:argv=""
+*/
+#include <iostream>
+#include <exception>
+#include <chrono>
+
+
+template <int N>
+struct power_of
+{
+    enum {
+        value = power_of<(N+1)/2>::value * 2
+    };
+};
+
+template <>
+struct power_of<2>
+{
+    enum {
+        value = 2
+    };
+};
+
+template <>
+struct power_of<1>
+{
+    enum {
+        value = 1
+    };
+};
+
+template <>
+struct power_of<0>
+{
+    enum {
+        value = 0
+    };
+};
+
+template <int N>
+void test()
+{
+    std::cout << N << "=> " << power_of<N>::value <<std::endl;
+}
+
+int main ( void )
+{try{
+    auto begin = std::chrono::high_resolution_clock::now();
+
+
+    test<0>();
+    test<1>();
+    test<2>();
+    test<3>();
+    test<4>();
+    test<5>();
+    test<6>();
+    test<7>();
+    test<8>();
+    test<9>();
+    test<127>();
+    test<128>();
+    test<129>();
+    //......
+
+    auto end = std::chrono::high_resolution_clock::now();
+    std::chrono::duration<double> seconds = end - begin;
+    std::cout << "Time: " << seconds.count() << std::endl;
+    return 0;
+}
+catch ( const std::exception& e )
+{
+    std::cerr << std::endl
+            << "std::exception(\"" << e.what() << "\")." << std::endl;
+    return 2;
+}
+catch ( ... )
+{
+    std::cerr  << std::endl
+            << "unknown exception." << std::endl;
+    return 1;
+}}
+