2022-20

lib/include/aocpp/DivMod.hpp

@@ -0,0 +1,50 @@
+#ifndef AOCPP_DIVMOD_HPP_
+#define AOCPP_DIVMOD_HPP_
+
+#include <tuple>
+
+#include "../doctest.h"
+
+namespace aocpp {
+
+template <typename T>
+auto DivMod(T dividend, T divisor) -> std::pair<T, T>
+{
+  auto const quotient  = dividend / divisor;
+  auto const remainder = dividend % divisor;
+  if (remainder == 0 || (remainder > 0) == (divisor > 0)) {
+    return {quotient, remainder};
+  } else {
+    return {quotient - 1, remainder + divisor};
+  }
+}
+
+template <typename T>
+auto Mod(T dividend, T divisor) -> T
+{
+  return DivMod(dividend, divisor).second;
+}
+
+template <typename T>
+auto Div(T dividend, T divisor) -> T
+{
+  return DivMod(dividend, divisor).first;
+}
+
+TEST_SUITE("divmod.hpp") {
+  TEST_CASE("DivMod behavior") {
+    CHECK(DivMod<int>(2,5) == std::make_pair(0,2));
+    CHECK(DivMod<int>(-2,5) == std::make_pair(-1,3));
+    CHECK(DivMod<int>(2,-5) == std::make_pair(-1,-3));
+    CHECK(DivMod<int>(-2,-5) == std::make_pair(0,-2));
+    
+    CHECK(DivMod<int>(-5,-5) == std::make_pair(1,0));
+    CHECK(DivMod<int>(-5,5) == std::make_pair(-1,0));
+    CHECK(DivMod<int>(5,-5) == std::make_pair(-1,0));
+    CHECK(DivMod<int>(-5,-5) == std::make_pair(1,0));
+  }
+}
+
+}
+
+#endif